third-party/leptonica/src/pngio.c
/*====================================================================*
- Copyright (C) 2001 Leptonica. All rights reserved.
-
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
- 1. Redistributions of source code must retain the above copyright
- notice, this list of conditions and the following disclaimer.
- 2. Redistributions in binary form must reproduce the above
- copyright notice, this list of conditions and the following
- disclaimer in the documentation and/or other materials
- provided with the distribution.
-
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ANY
- CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*====================================================================*/
/*
* pngio.c
*
* Read png from file
* PIX *pixReadStreamPng()
* l_int32 readHeaderPng()
* l_int32 freadHeaderPng()
* l_int32 readHeaderMemPng()
* l_int32 fgetPngResolution()
* l_int32 isPngInterlaced()
* l_int32 fgetPngColormapInfo()
*
* Write png to file
* l_int32 pixWritePng() [ special top level ]
* l_int32 pixWriteStreamPng()
* l_int32 pixSetZlibCompression()
*
* Setting flag for special read mode
* void l_pngSetReadStrip16To8()
*
* Read/write to memory
* PIX *pixReadMemPng()
* l_int32 pixWriteMemPng()
*
* Documentation: libpng.txt and example.c
*
* On input (decompression from file), palette color images
* are read into an 8 bpp Pix with a colormap, and 24 bpp
* 3 component color images are read into a 32 bpp Pix with
* rgb samples. On output (compression to file), palette color
* images are written as 8 bpp with the colormap, and 32 bpp
* full color images are written compressed as a 24 bpp,
* 3 component color image.
*
* In the following, we use these abbreviations:
* bps == bit/sample
* spp == samples/pixel
* bpp == bits/pixel of image in Pix (memory)
* where each component is referred to as a "sample".
*
* For reading and writing rgb and rgba images, we read and write
* alpha if it exists (spp == 4) and do not read or write if
* it doesn't (spp == 3). The alpha component can be 'removed'
* simply by setting spp to 3. In leptonica, we make relatively
* little explicit use of the alpha sample. Note that the alpha
* sample in the image is also called "alpha transparency",
* "alpha component" and "alpha layer."
*
* To change the zlib compression level, use pixSetZlibCompression()
* before writing the file. The default is for standard png compression.
* The zlib compression value can be set [0 ... 9], with
* 0 no compression (huge files)
* 1 fastest compression
* -1 default compression (equivalent to 6 in latest version)
* 9 best compression
* Note that if you are using the defined constants in zlib instead
* of the compression integers given above, you must include zlib.h.
*
* There is global for determining the size of retained samples:
* var_PNG_STRIP_16_to_8
* and a function l_pngSetReadStrip16To8() for setting it.
* The default is TRUE, which causes pixRead() to strip each 16 bit
* sample down to 8 bps:
* - For 16 bps rgb (16 bps, 3 spp) --> 32 bpp rgb Pix
* - For 16 bps gray (16 bps, 1 spp) --> 8 bpp grayscale Pix
* If the variable is set to FALSE, the 16 bit gray samples
* are saved when read; the 16 bit rgb samples return an error.
* Note: results can be non-deterministic if used with
* multi-threaded applications.
*
* On systems like windows without fmemopen() and open_memstream(),
* we write data to a temp file and read it back for operations
* between pix and compressed-data, such as pixReadMemPng() and
* pixWriteMemPng().
*/
#include <string.h>
#include "allheaders.h"
#ifdef HAVE_CONFIG_H
#include "config_auto.h"
#endif /* HAVE_CONFIG_H */
/* --------------------------------------------*/
#if HAVE_LIBPNG /* defined in environ.h */
/* --------------------------------------------*/
#include "png.h"
#if HAVE_LIBZ
#include "zlib.h"
#else
#define Z_DEFAULT_COMPRESSION (-1)
#endif /* HAVE_LIBZ */
/* ------------------ Set default for read option -------------------- */
/* Strip 16 bpp --> 8 bpp on reading png; default is for stripping.
* If you don't strip, you can't read the gray-alpha spp = 2 images. */
static l_int32 var_PNG_STRIP_16_TO_8 = 1;
#ifndef NO_CONSOLE_IO
#define DEBUG_READ 0
#define DEBUG_WRITE 0
#endif /* ~NO_CONSOLE_IO */
/*---------------------------------------------------------------------*
* Reading png *
*---------------------------------------------------------------------*/
/*!
* pixReadStreamPng()
*
* Input: stream
* Return: pix, or null on error
*
* Notes:
* (1) If called from pixReadStream(), the stream is positioned
* at the beginning of the file.
* (2) To do sequential reads of png format images from a stream,
* use pixReadStreamPng()
* (3) Any image with alpha is converted to RGBA (spp = 4, with
* equal red, green and blue channels) on reading.
* There are three important cases with alpha:
* (a) grayscale-with-alpha (spp = 2), where bpp = 8, and each
* pixel has an associated alpha (transparency) value
* in the second component of the image data.
* (b) spp = 1, d = 1 with colormap and alpha in the trans array.
* Transparency is usually associated with the white background.
* (c) spp = 1, d = 8 with colormap and alpha in the trans array.
* Each color in the colormap has a separate transparency value.
* (4) We use the high level png interface, where the transforms are set
* up in advance and the header and image are read with a single
* call. The more complicated interface, where the header is
* read first and the buffers for the raster image are user-
* allocated before reading the image, works for single images,
* but I could not get it to work properly for the successive
* png reads that are required by pixaReadStream().
*/
PIX *
pixReadStreamPng(FILE *fp)
{
l_uint8 byte;
l_int32 rval, gval, bval;
l_int32 i, j, k, index, ncolors, bitval;
l_int32 wpl, d, spp, cindex, tRNS;
l_uint32 png_transforms;
l_uint32 *data, *line, *ppixel;
int num_palette, num_text, num_trans;
png_byte bit_depth, color_type, channels;
png_uint_32 w, h, rowbytes;
png_uint_32 xres, yres;
png_bytep rowptr, trans;
png_bytep *row_pointers;
png_structp png_ptr;
png_infop info_ptr, end_info;
png_colorp palette;
png_textp text_ptr; /* ptr to text_chunk */
PIX *pix, *pixt;
PIXCMAP *cmap;
PROCNAME("pixReadStreamPng");
if (!fp)
return (PIX *)ERROR_PTR("fp not defined", procName, NULL);
pix = NULL;
/* Allocate the 3 data structures */
if ((png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
(png_voidp)NULL, NULL, NULL)) == NULL)
return (PIX *)ERROR_PTR("png_ptr not made", procName, NULL);
if ((info_ptr = png_create_info_struct(png_ptr)) == NULL) {
png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
return (PIX *)ERROR_PTR("info_ptr not made", procName, NULL);
}
if ((end_info = png_create_info_struct(png_ptr)) == NULL) {
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
return (PIX *)ERROR_PTR("end_info not made", procName, NULL);
}
/* Set up png setjmp error handling */
if (setjmp(png_jmpbuf(png_ptr))) {
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
return (PIX *)ERROR_PTR("internal png error", procName, NULL);
}
png_init_io(png_ptr, fp);
/* ---------------------------------------------------------- *
* Set the transforms flags. Whatever happens here,
* NEVER invert 1 bpp using PNG_TRANSFORM_INVERT_MONO.
* Also, do not use PNG_TRANSFORM_EXPAND, which would
* expand all images with bpp < 8 to 8 bpp.
* ---------------------------------------------------------- */
/* To strip 16 --> 8 bit depth, use PNG_TRANSFORM_STRIP_16 */
if (var_PNG_STRIP_16_TO_8 == 1) { /* our default */
png_transforms = PNG_TRANSFORM_STRIP_16;
} else {
png_transforms = PNG_TRANSFORM_IDENTITY;
L_INFO("not stripping 16 --> 8 in png reading\n", procName);
}
/* Read it */
png_read_png(png_ptr, info_ptr, png_transforms, NULL);
row_pointers = png_get_rows(png_ptr, info_ptr);
w = png_get_image_width(png_ptr, info_ptr);
h = png_get_image_height(png_ptr, info_ptr);
bit_depth = png_get_bit_depth(png_ptr, info_ptr);
rowbytes = png_get_rowbytes(png_ptr, info_ptr);
color_type = png_get_color_type(png_ptr, info_ptr);
channels = png_get_channels(png_ptr, info_ptr);
spp = channels;
tRNS = png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS) ? 1 : 0;
if (spp == 1) {
d = bit_depth;
} else { /* spp == 2 (gray + alpha), spp == 3 (rgb), spp == 4 (rgba) */
d = 4 * bit_depth;
}
/* Remove if/when this is implemented for all bit_depths */
if (spp == 3 && bit_depth != 8) {
fprintf(stderr, "Help: spp = 3 and depth = %d != 8\n!!", bit_depth);
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
return (PIX *)ERROR_PTR("not implemented for this depth",
procName, NULL);
}
if (color_type == PNG_COLOR_TYPE_PALETTE ||
color_type == PNG_COLOR_MASK_PALETTE) { /* generate a colormap */
png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette);
cmap = pixcmapCreate(d); /* spp == 1 */
for (cindex = 0; cindex < num_palette; cindex++) {
rval = palette[cindex].red;
gval = palette[cindex].green;
bval = palette[cindex].blue;
pixcmapAddColor(cmap, rval, gval, bval);
}
} else {
cmap = NULL;
}
if ((pix = pixCreate(w, h, d)) == NULL) {
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
return (PIX *)ERROR_PTR("pix not made", procName, NULL);
}
wpl = pixGetWpl(pix);
data = pixGetData(pix);
pixSetColormap(pix, cmap);
pixSetSpp(pix, spp);
if (spp == 1 && !tRNS) { /* copy straight from buffer to pix */
for (i = 0; i < h; i++) {
line = data + i * wpl;
rowptr = row_pointers[i];
for (j = 0; j < rowbytes; j++) {
SET_DATA_BYTE(line, j, rowptr[j]);
}
}
} else if (spp == 2) { /* grayscale + alpha; convert to RGBA */
L_INFO("converting (gray + alpha) ==> RGBA\n", procName);
for (i = 0; i < h; i++) {
ppixel = data + i * wpl;
rowptr = row_pointers[i];
for (j = k = 0; j < w; j++) {
/* Copy gray value into r, g and b */
SET_DATA_BYTE(ppixel, COLOR_RED, rowptr[k]);
SET_DATA_BYTE(ppixel, COLOR_GREEN, rowptr[k]);
SET_DATA_BYTE(ppixel, COLOR_BLUE, rowptr[k++]);
SET_DATA_BYTE(ppixel, L_ALPHA_CHANNEL, rowptr[k++]);
ppixel++;
}
}
pixSetSpp(pix, 4); /* we do not support 2 spp pix */
} else if (spp == 3 || spp == 4) {
for (i = 0; i < h; i++) {
ppixel = data + i * wpl;
rowptr = row_pointers[i];
for (j = k = 0; j < w; j++) {
SET_DATA_BYTE(ppixel, COLOR_RED, rowptr[k++]);
SET_DATA_BYTE(ppixel, COLOR_GREEN, rowptr[k++]);
SET_DATA_BYTE(ppixel, COLOR_BLUE, rowptr[k++]);
if (spp == 4)
SET_DATA_BYTE(ppixel, L_ALPHA_CHANNEL, rowptr[k++]);
ppixel++;
}
}
}
/* Special spp == 1 cases with transparency:
* (1) 8 bpp without colormap; assume full transparency
* (2) 1 bpp with colormap + trans array (for alpha)
* (3) 8 bpp with colormap + trans array (for alpha)
* These all require converting to RGBA */
if (spp == 1 && tRNS) {
if (!cmap) {
/* Case 1: make fully transparent RGBA image */
L_INFO("transparency, 1 spp, no colormap, no transparency array: "
"convention is fully transparent image\n", procName);
L_INFO("converting (fully transparent 1 spp) ==> RGBA\n", procName);
pixDestroy(&pix);
pix = pixCreate(w, h, 32); /* init to alpha = 0 (transparent) */
pixSetSpp(pix, 4);
} else {
L_INFO("converting (cmap + alpha) ==> RGBA\n", procName);
/* Grab the transparency array */
png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, NULL);
if (!trans) { /* invalid png file */
pixDestroy(&pix);
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
return (PIX *)ERROR_PTR("cmap, tRNS, but no transparency array",
procName, NULL);
}
/* Save the cmap and destroy the pix */
cmap = pixcmapCopy(pixGetColormap(pix));
ncolors = pixcmapGetCount(cmap);
pixDestroy(&pix);
/* Start over with 32 bit RGBA */
pix = pixCreate(w, h, 32);
wpl = pixGetWpl(pix);
data = pixGetData(pix);
pixSetSpp(pix, 4);
#if DEBUG_READ
fprintf(stderr, "ncolors = %d, num_trans = %d\n",
ncolors, num_trans);
for (i = 0; i < ncolors; i++) {
pixcmapGetColor(cmap, i, &rval, &gval, &bval);
if (i < num_trans) {
fprintf(stderr, "(r,g,b,a) = (%d,%d,%d,%d)\n",
rval, gval, bval, trans[i]);
} else {
fprintf(stderr, "(r,g,b,a) = (%d,%d,%d,<<255>>)\n",
rval, gval, bval);
}
}
#endif /* DEBUG_READ */
/* Extract the data and convert to RGBA */
if (d == 1) {
/* Case 2: 1 bpp with transparency (usually) behind white */
L_INFO("converting 1 bpp cmap with alpha ==> RGBA\n", procName);
if (num_trans == 1)
L_INFO("num_trans = 1; second color opaque by default\n",
procName);
for (i = 0; i < h; i++) {
ppixel = data + i * wpl;
rowptr = row_pointers[i];
for (j = 0, index = 0; j < rowbytes; j++) {
byte = rowptr[j];
for (k = 0; k < 8 && index < w; k++, index++) {
bitval = (byte >> (7 - k)) & 1;
pixcmapGetColor(cmap, bitval, &rval, &gval, &bval);
composeRGBPixel(rval, gval, bval, ppixel);
SET_DATA_BYTE(ppixel, L_ALPHA_CHANNEL,
bitval < num_trans ? trans[bitval] : 255);
ppixel++;
}
}
}
} else if (d == 8) {
/* Case 3: 8 bpp with cmap and associated transparency */
L_INFO("converting 8 bpp cmap with alpha ==> RGBA\n", procName);
for (i = 0; i < h; i++) {
ppixel = data + i * wpl;
rowptr = row_pointers[i];
for (j = 0; j < w; j++) {
index = rowptr[j];
pixcmapGetColor(cmap, index, &rval, &gval, &bval);
composeRGBPixel(rval, gval, bval, ppixel);
/* Assume missing entries to be 255 (opaque)
* according to the spec:
* http://www.w3.org/TR/PNG/#11tRNS */
SET_DATA_BYTE(ppixel, L_ALPHA_CHANNEL,
index < num_trans ? trans[index] : 255);
ppixel++;
}
}
} else {
L_ERROR("spp == 1, cmap, trans array, invalid depth: %d\n",
procName, d);
}
pixcmapDestroy(&cmap);
}
}
#if DEBUG_READ
if (cmap) {
for (i = 0; i < 16; i++) {
fprintf(stderr, "[%d] = %d\n", i,
((l_uint8 *)(cmap->array))[i]);
}
}
#endif /* DEBUG_READ */
/* Final adjustments for bpp = 1.
* + If there is no colormap, the image must be inverted because
* png stores black pixels as 0.
* + We have already handled the case of cmapped, 1 bpp pix
* with transparency, where the output pix is 32 bpp RGBA.
* If there is no transparency but the pix has a colormap,
* we remove the colormap, because functions operating on
* 1 bpp images in leptonica assume no colormap.
* + The colormap must be removed in such a way that the pixel
* values are not changed. If the values are only black and
* white, we return a 1 bpp image; if gray, return an 8 bpp pix;
* otherwise, return a 32 bpp rgb pix.
*
* Note that we cannot use the PNG_TRANSFORM_INVERT_MONO flag
* to do the inversion, because that flag (since version 1.0.9)
* inverts 8 bpp grayscale as well, which we don't want to do.
* (It also doesn't work if there is a colormap.)
*
* Note that if the input png is a 1-bit with colormap and
* transparency, it has already been rendered as a 32 bpp,
* spp = 4 rgba pix.
*/
if (pixGetDepth(pix) == 1) {
if (!cmap) {
pixInvert(pix, pix);
} else {
pixt = pixRemoveColormap(pix, REMOVE_CMAP_BASED_ON_SRC);
pixDestroy(&pix);
pix = pixt;
}
}
xres = png_get_x_pixels_per_meter(png_ptr, info_ptr);
yres = png_get_y_pixels_per_meter(png_ptr, info_ptr);
pixSetXRes(pix, (l_int32)((l_float32)xres / 39.37 + 0.5)); /* to ppi */
pixSetYRes(pix, (l_int32)((l_float32)yres / 39.37 + 0.5)); /* to ppi */
/* Get the text if there is any */
png_get_text(png_ptr, info_ptr, &text_ptr, &num_text);
if (num_text && text_ptr)
pixSetText(pix, text_ptr->text);
png_destroy_read_struct(&png_ptr, &info_ptr, &end_info);
return pix;
}
/*!
* readHeaderPng()
*
* Input: filename
* &w (<optional return>)
* &h (<optional return>)
* &bps (<optional return>, bits/sample)
* &spp (<optional return>, samples/pixel)
* &iscmap (<optional return>)
* Return: 0 if OK, 1 on error
*
* Notes:
* (1) If there is a colormap, iscmap is returned as 1; else 0.
* (2) For gray+alpha, although the png records bps = 16, we
* consider this as two 8 bpp samples (gray and alpha).
* When a gray+alpha is read, it is converted to 32 bpp RGBA.
*/
l_int32
readHeaderPng(const char *filename,
l_int32 *pw,
l_int32 *ph,
l_int32 *pbps,
l_int32 *pspp,
l_int32 *piscmap)
{
l_int32 ret;
FILE *fp;
PROCNAME("readHeaderPng");
if (pw) *pw = 0;
if (ph) *ph = 0;
if (pbps) *pbps = 0;
if (pspp) *pspp = 0;
if (piscmap) *piscmap = 0;
if (!filename)
return ERROR_INT("filename not defined", procName, 1);
if ((fp = fopenReadStream(filename)) == NULL)
return ERROR_INT("image file not found", procName, 1);
ret = freadHeaderPng(fp, pw, ph, pbps, pspp, piscmap);
fclose(fp);
return ret;
}
/*!
* freadHeaderPng()
*
* Input: stream
* &w (<optional return>)
* &h (<optional return>)
* &bps (<optional return>, bits/sample)
* &spp (<optional return>, samples/pixel)
* &iscmap (<optional return>)
* Return: 0 if OK, 1 on error
*
* Notes:
* (1) See readHeaderPng(). We only need the first 40 bytes in the file.
*/
l_int32
freadHeaderPng(FILE *fp,
l_int32 *pw,
l_int32 *ph,
l_int32 *pbps,
l_int32 *pspp,
l_int32 *piscmap)
{
l_int32 nbytes, ret;
l_uint8 *data;
PROCNAME("freadHeaderPng");
if (pw) *pw = 0;
if (ph) *ph = 0;
if (pbps) *pbps = 0;
if (pspp) *pspp = 0;
if (piscmap) *piscmap = 0;
if (!fp)
return ERROR_INT("stream not defined", procName, 1);
nbytes = fnbytesInFile(fp);
if (nbytes < 40)
return ERROR_INT("file too small to be png", procName, 1);
if ((data = (l_uint8 *)CALLOC(40, sizeof(l_uint8))) == NULL)
return ERROR_INT("CALLOC fail for data", procName, 1);
if (fread(data, 1, 40, fp) != 40)
return ERROR_INT("error reading data", procName, 1);
ret = readHeaderMemPng(data, 40, pw, ph, pbps, pspp, piscmap);
FREE(data);
return ret;
}
/*!
* readHeaderMemPng()
*
* Input: data
* size (40 bytes is sufficient)
* &w (<optional return>)
* &h (<optional return>)
* &bps (<optional return>, bits/sample)
* &spp (<optional return>, samples/pixel)
* &iscmap (<optional return>; input NULL to ignore)
* Return: 0 if OK, 1 on error
*
* Notes:
* (1) See readHeaderPng().
* (2) png colortypes (see png.h: PNG_COLOR_TYPE_*):
* 0: gray; fully transparent (with tRNS) (1 spp)
* 2: RGB (3 spp)
* 3: colormap; colormap+alpha (with tRNS) (1 spp)
* 4: gray + alpha (2 spp)
* 6: RGBA (4 spp)
* Note:
* 0 and 3 have the alpha information in a tRNS chunk
* 4 and 6 have separate alpha samples with each pixel.
*/
l_int32
readHeaderMemPng(const l_uint8 *data,
size_t size,
l_int32 *pw,
l_int32 *ph,
l_int32 *pbps,
l_int32 *pspp,
l_int32 *piscmap)
{
l_uint16 twobytes;
l_uint16 *pshort;
l_int32 colortype, bps, spp;
l_uint32 *pword;
PROCNAME("readHeaderMemPng");
if (pw) *pw = 0;
if (ph) *ph = 0;
if (pbps) *pbps = 0;
if (pspp) *pspp = 0;
if (piscmap) *piscmap = 0;
if (!data)
return ERROR_INT("data not defined", procName, 1);
if (size < 40)
return ERROR_INT("size < 40", procName, 1);
/* Check password */
if (data[0] != 137 || data[1] != 80 || data[2] != 78 ||
data[3] != 71 || data[4] != 13 || data[5] != 10 ||
data[6] != 26 || data[7] != 10)
return ERROR_INT("not a valid png file", procName, 1);
pword = (l_uint32 *)data;
pshort = (l_uint16 *)data;
if (pw) *pw = convertOnLittleEnd32(pword[4]);
if (ph) *ph = convertOnLittleEnd32(pword[5]);
twobytes = convertOnLittleEnd16(pshort[12]); /* contains depth/sample */
/* and the color type */
colortype = twobytes & 0xff; /* color type */
bps = twobytes >> 8; /* bits/sample */
/* Special case with alpha that is extracted as RGBA.
* Note that the cmap+alpha is also extracted as RGBA,
* but only if the tRNS chunk exists, which we can't tell
* by this simple parser.*/
if (colortype == 4)
L_INFO("gray + alpha: will extract as RGBA (spp = 4)\n", procName);
if (colortype == 2) { /* RGB */
spp = 3;
} else if (colortype == 6) { /* RGBA */
spp = 4;
} else if (colortype == 4) { /* gray + alpha */
spp = 2;
bps = 8; /* both the gray and alpha are 8-bit samples */
} else { /* gray (0) or cmap (3) or cmap+alpha (3) */
spp = 1;
}
if (pbps) *pbps = bps;
if (pspp) *pspp = spp;
if (piscmap) {
if (colortype & 1) /* palette */
*piscmap = 1;
else
*piscmap = 0;
}
return 0;
}
/*
* fgetPngResolution()
*
* Input: stream (opened for read)
* &xres, &yres (<return> resolution in ppi)
* Return: 0 if OK; 1 on error
*
* Notes:
* (1) If neither resolution field is set, this is not an error;
* the returned resolution values are 0 (designating 'unknown').
* (2) Side-effect: this rewinds the stream.
*/
l_int32
fgetPngResolution(FILE *fp,
l_int32 *pxres,
l_int32 *pyres)
{
png_uint_32 xres, yres;
png_structp png_ptr;
png_infop info_ptr;
PROCNAME("fgetPngResolution");
if (pxres) *pxres = 0;
if (pyres) *pyres = 0;
if (!fp)
return ERROR_INT("stream not opened", procName, 1);
if (!pxres || !pyres)
return ERROR_INT("&xres and &yres not both defined", procName, 1);
/* Make the two required structs */
if ((png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
(png_voidp)NULL, NULL, NULL)) == NULL)
return ERROR_INT("png_ptr not made", procName, 1);
if ((info_ptr = png_create_info_struct(png_ptr)) == NULL) {
png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
return ERROR_INT("info_ptr not made", procName, 1);
}
/* Set up png setjmp error handling.
* Without this, an error calls exit. */
if (setjmp(png_jmpbuf(png_ptr))) {
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
return ERROR_INT("internal png error", procName, 1);
}
/* Read the metadata */
rewind(fp);
png_init_io(png_ptr, fp);
png_read_png(png_ptr, info_ptr, 0, NULL);
xres = png_get_x_pixels_per_meter(png_ptr, info_ptr);
yres = png_get_y_pixels_per_meter(png_ptr, info_ptr);
*pxres = (l_int32)((l_float32)xres / 39.37 + 0.5); /* to ppi */
*pyres = (l_int32)((l_float32)yres / 39.37 + 0.5);
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
rewind(fp);
return 0;
}
/*!
* isPngInterlaced()
*
* Input: filename
* &interlaced (<return> 1 if interlaced png; 0 otherwise)
* Return: 0 if OK, 1 on error
*/
l_int32
isPngInterlaced(const char *filename,
l_int32 *pinterlaced)
{
l_uint8 buf[32];
FILE *fp;
PROCNAME("isPngInterlaced");
if (!pinterlaced)
return ERROR_INT("&interlaced not defined", procName, 1);
*pinterlaced = 0;
if (!filename)
return ERROR_INT("filename not defined", procName, 1);
if ((fp = fopenReadStream(filename)) == NULL)
return ERROR_INT("stream not opened", procName, 1);
if (fread(buf, 1, 32, fp) != 32)
return ERROR_INT("data not read", procName, 1);
fclose(fp);
*pinterlaced = (buf[28] == 0) ? 0 : 1;
return 0;
}
/*
* fgetPngColormapInfo()
*
* Input: stream (opened for read)
* &cmap (optional <return>; use NULL to skip)
* &transparency (optional <return> 1 if colormapped with
* transparency, 0 otherwise; use NULL to skip)
* Return: 0 if OK; 1 on error
*
* Notes:
* (1) The transparency information in a png is in the tRNA array,
* which is separate from the colormap. If this array exists
* and if any element is less than 255, there exists some
* transparency.
* (2) Side-effect: this rewinds the stream.
*/
l_int32
fgetPngColormapInfo(FILE *fp,
PIXCMAP **pcmap,
l_int32 *ptransparency)
{
l_int32 i, cindex, rval, gval, bval, num_palette, num_trans;
png_byte bit_depth, color_type;
png_bytep trans;
png_colorp palette;
png_structp png_ptr;
png_infop info_ptr;
PROCNAME("fgetPngColormapInfo");
if (pcmap) *pcmap = NULL;
if (ptransparency) *ptransparency = 0;
if (!pcmap && !ptransparency)
return ERROR_INT("no output defined", procName, 1);
if (!fp)
return ERROR_INT("stream not opened", procName, 1);
/* Make the two required structs */
if ((png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
(png_voidp)NULL, NULL, NULL)) == NULL)
return ERROR_INT("png_ptr not made", procName, 1);
if ((info_ptr = png_create_info_struct(png_ptr)) == NULL) {
png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
return ERROR_INT("info_ptr not made", procName, 1);
}
/* Set up png setjmp error handling.
* Without this, an error calls exit. */
if (setjmp(png_jmpbuf(png_ptr))) {
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
return ERROR_INT("internal png error", procName, 1);
}
/* Read the metadata and check if there is a colormap */
rewind(fp);
png_init_io(png_ptr, fp);
png_read_png(png_ptr, info_ptr, 0, NULL);
color_type = png_get_color_type(png_ptr, info_ptr);
if (color_type != PNG_COLOR_TYPE_PALETTE &&
color_type != PNG_COLOR_MASK_PALETTE) {
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
return 0;
}
/* Optionally, read the colormap */
if (pcmap) {
bit_depth = png_get_bit_depth(png_ptr, info_ptr);
png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette);
*pcmap = pixcmapCreate(bit_depth); /* spp == 1 */
for (cindex = 0; cindex < num_palette; cindex++) {
rval = palette[cindex].red;
gval = palette[cindex].green;
bval = palette[cindex].blue;
pixcmapAddColor(*pcmap, rval, gval, bval);
}
}
/* Optionally, look for transparency. Note that the colormap
* has been initialized to fully opaque. */
if (ptransparency && png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, NULL);
if (trans) {
for (i = 0; i < num_trans; i++) {
if (trans[i] < 255) { /* not fully opaque */
*ptransparency = 1;
if (pcmap) pixcmapSetAlpha(*pcmap, i, trans[i]);
}
}
} else {
L_ERROR("transparency array not returned\n", procName);
}
}
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
rewind(fp);
return 0;
}
/*---------------------------------------------------------------------*
* Writing png *
*---------------------------------------------------------------------*/
/*!
* pixWritePng()
*
* Input: filename
* pix
* gamma
* Return: 0 if OK; 1 on error
*
* Notes:
* (1) Special version for writing png with a specified gamma.
* When using pixWrite(), no field is given for gamma.
*/
l_int32
pixWritePng(const char *filename,
PIX *pix,
l_float32 gamma)
{
FILE *fp;
PROCNAME("pixWritePng");
if (!pix)
return ERROR_INT("pix not defined", procName, 1);
if (!filename)
return ERROR_INT("filename not defined", procName, 1);
if ((fp = fopenWriteStream(filename, "wb+")) == NULL)
return ERROR_INT("stream not opened", procName, 1);
if (pixWriteStreamPng(fp, pix, gamma)) {
fclose(fp);
return ERROR_INT("pix not written to stream", procName, 1);
}
fclose(fp);
return 0;
}
/*!
* pixWriteStreamPng()
*
* Input: stream
* pix
* gamma (use 0.0 if gamma is not defined)
* Return: 0 if OK; 1 on error
*
* Notes:
* (1) If called from pixWriteStream(), the stream is positioned
* at the beginning of the file.
* (2) To do sequential writes of png format images to a stream,
* use pixWriteStreamPng() directly.
* (3) gamma is an optional png chunk. If no gamma value is to be
* placed into the file, use gamma = 0.0. Otherwise, if
* gamma > 0.0, its value is written into the header.
* (4) The use of gamma in png is highly problematic. For an illuminating
* discussion, see: http://hsivonen.iki.fi/png-gamma/
* (5) What is the effect/meaning of gamma in the png file? This
* gamma, which we can call the 'source' gamma, is the
* inverse of the gamma that was used in enhance.c to brighten
* or darken images. The 'source' gamma is supposed to indicate
* the intensity mapping that was done at the time the
* image was captured. Display programs typically apply a
* 'display' gamma of 2.2 to the output, which is intended
* to linearize the intensity based on the response of
* thermionic tubes (CRTs). Flat panel LCDs have typically
* been designed to give a similar response as CRTs (call it
* "backward compatibility"). The 'display' gamma is
* in some sense the inverse of the 'source' gamma.
* jpeg encoders attached to scanners and cameras will lighten
* the pixels, applying a gamma corresponding to approximately
* a square-root relation of output vs input:
* output = input^(gamma)
* where gamma is often set near 0.4545 (1/gamma is 2.2).
* This is stored in the image file. Then if the display
* program reads the gamma, it will apply a display gamma,
* typically about 2.2; the product is 1.0, and the
* display program produces a linear output. This works because
* the dark colors were appropriately boosted by the scanner,
* as described by the 'source' gamma, so they should not
* be further boosted by the display program.
* (6) As an example, with xv and display, if no gamma is stored,
* the program acts as if gamma were 0.4545, multiplies this by 2.2,
* and does a linear rendering. Taking this as a baseline
* brightness, if the stored gamma is:
* > 0.4545, the image is rendered lighter than baseline
* < 0.4545, the image is rendered darker than baseline
* In contrast, gqview seems to ignore the gamma chunk in png.
* (7) The only valid pixel depths in leptonica are 1, 2, 4, 8, 16
* and 32. However, it is possible, and in some cases desirable,
* to write out a png file using an rgb pix that has 24 bpp.
* For example, the open source xpdf SplashBitmap class generates
* 24 bpp rgb images. Consequently, we enable writing 24 bpp pix.
* To generate such a pix, you can make a 24 bpp pix without data
* and assign the data array to the pix; e.g.,
* pix = pixCreateHeader(w, h, 24);
* pixSetData(pix, rgbdata);
* See pixConvert32To24() for an example, where we get rgbdata
* from the 32 bpp pix. Caution: do not call pixSetPadBits(),
* because the alignment is wrong and you may erase part of the
* last pixel on each line.
* (8) If the pix has a colormap, it is written to file. In most
* situations, the alpha component is 255 for each colormap entry,
* which is opaque and indicates that it should be ignored.
* However, if any alpha component is not 255, it is assumed that
* the alpha values are valid, and they are written to the png
* file in a tRNS segment. On readback, the tRNS segment is
* identified, and the colormapped image with alpha is converted
* to a 4 spp rgba image.
*/
l_int32
pixWriteStreamPng(FILE *fp,
PIX *pix,
l_float32 gamma)
{
char commentstring[] = "Comment";
l_int32 i, j, k;
l_int32 wpl, d, spp, cmflag, opaque;
l_int32 ncolors, compval;
l_int32 *rmap, *gmap, *bmap, *amap;
l_uint32 *data, *ppixel;
png_byte bit_depth, color_type;
png_byte alpha[256];
png_uint_32 w, h;
png_uint_32 xres, yres;
png_bytep *row_pointers;
png_bytep rowbuffer;
png_structp png_ptr;
png_infop info_ptr;
png_colorp palette;
PIX *pixt;
PIXCMAP *cmap;
char *text;
PROCNAME("pixWriteStreamPng");
if (!fp)
return ERROR_INT("stream not open", procName, 1);
if (!pix)
return ERROR_INT("pix not defined", procName, 1);
/* Allocate the 2 data structures */
if ((png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING,
(png_voidp)NULL, NULL, NULL)) == NULL)
return ERROR_INT("png_ptr not made", procName, 1);
if ((info_ptr = png_create_info_struct(png_ptr)) == NULL) {
png_destroy_write_struct(&png_ptr, (png_infopp)NULL);
return ERROR_INT("info_ptr not made", procName, 1);
}
/* Set up png setjmp error handling */
if (setjmp(png_jmpbuf(png_ptr))) {
png_destroy_write_struct(&png_ptr, &info_ptr);
return ERROR_INT("internal png error", procName, 1);
}
png_init_io(png_ptr, fp);
/* With best zlib compression (9), get between 1 and 10% improvement
* over default (6), but the compression is 3 to 10 times slower.
* Use the zlib default (6) as our default compression unless
* pix->special falls in the range [10 ... 19]; then subtract 10
* to get the compression value. */
compval = Z_DEFAULT_COMPRESSION;
if (pix->special >= 10 && pix->special < 20)
compval = pix->special - 10;
png_set_compression_level(png_ptr, compval);
w = pixGetWidth(pix);
h = pixGetHeight(pix);
d = pixGetDepth(pix);
spp = pixGetSpp(pix);
if ((cmap = pixGetColormap(pix)))
cmflag = 1;
else
cmflag = 0;
/* Set the color type and bit depth. */
if (d == 32 && spp == 4) {
bit_depth = 8;
color_type = PNG_COLOR_TYPE_RGBA; /* 6 */
cmflag = 0; /* ignore if it exists */
} else if (d == 24 || d == 32) {
bit_depth = 8;
color_type = PNG_COLOR_TYPE_RGB; /* 2 */
cmflag = 0; /* ignore if it exists */
} else {
bit_depth = d;
color_type = PNG_COLOR_TYPE_GRAY; /* 0 */
}
if (cmflag)
color_type = PNG_COLOR_TYPE_PALETTE; /* 3 */
#if DEBUG_WRITE
fprintf(stderr, "cmflag = %d, bit_depth = %d, color_type = %d\n",
cmflag, bit_depth, color_type);
#endif /* DEBUG_WRITE */
png_set_IHDR(png_ptr, info_ptr, w, h, bit_depth, color_type,
PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE,
PNG_FILTER_TYPE_BASE);
/* Store resolution in ppm, if known */
xres = (png_uint_32)(39.37 * (l_float32)pixGetXRes(pix) + 0.5);
yres = (png_uint_32)(39.37 * (l_float32)pixGetYRes(pix) + 0.5);
if ((xres == 0) || (yres == 0))
png_set_pHYs(png_ptr, info_ptr, 0, 0, PNG_RESOLUTION_UNKNOWN);
else
png_set_pHYs(png_ptr, info_ptr, xres, yres, PNG_RESOLUTION_METER);
if (cmflag) {
pixcmapToArrays(cmap, &rmap, &gmap, &bmap, &amap);
ncolors = pixcmapGetCount(cmap);
pixcmapIsOpaque(cmap, &opaque);
/* Make and save the palette */
if ((palette = (png_colorp)(CALLOC(ncolors, sizeof(png_color))))
== NULL)
return ERROR_INT("palette not made", procName, 1);
for (i = 0; i < ncolors; i++) {
palette[i].red = (png_byte)rmap[i];
palette[i].green = (png_byte)gmap[i];
palette[i].blue = (png_byte)bmap[i];
alpha[i] = (png_byte)amap[i];
}
png_set_PLTE(png_ptr, info_ptr, palette, (int)ncolors);
if (!opaque) /* alpha channel has some transparency; assume valid */
png_set_tRNS(png_ptr, info_ptr, (png_bytep)alpha,
(int)ncolors, NULL);
FREE(rmap);
FREE(gmap);
FREE(bmap);
FREE(amap);
}
/* 0.4545 is treated as the default by some image
* display programs (not gqview). A value > 0.4545 will
* lighten an image as displayed by xv, display, etc. */
if (gamma > 0.0)
png_set_gAMA(png_ptr, info_ptr, (l_float64)gamma);
if ((text = pixGetText(pix))) {
png_text text_chunk;
text_chunk.compression = PNG_TEXT_COMPRESSION_NONE;
text_chunk.key = commentstring;
text_chunk.text = text;
text_chunk.text_length = strlen(text);
#ifdef PNG_ITXT_SUPPORTED
text_chunk.itxt_length = 0;
text_chunk.lang = NULL;
text_chunk.lang_key = NULL;
#endif
png_set_text(png_ptr, info_ptr, &text_chunk, 1);
}
/* Write header and palette info */
png_write_info(png_ptr, info_ptr);
if ((d != 32) && (d != 24)) { /* not rgb color */
/* Generate a temporary pix with bytes swapped.
* For writing a 1 bpp image as png:
* - if no colormap, invert the data, because png writes
* black as 0
* - if colormapped, do not invert the data; the two RGBA
* colors can have any value. */
if (d == 1 && !cmap) {
pixt = pixInvert(NULL, pix);
pixEndianByteSwap(pixt);
} else {
pixt = pixEndianByteSwapNew(pix);
}
if (!pixt) {
png_destroy_write_struct(&png_ptr, &info_ptr);
return ERROR_INT("pixt not made", procName, 1);
}
/* Make and assign array of image row pointers */
if ((row_pointers = (png_bytep *)CALLOC(h, sizeof(png_bytep))) == NULL)
return ERROR_INT("row-pointers not made", procName, 1);
wpl = pixGetWpl(pixt);
data = pixGetData(pixt);
for (i = 0; i < h; i++)
row_pointers[i] = (png_bytep)(data + i * wpl);
png_set_rows(png_ptr, info_ptr, row_pointers);
/* Transfer the data */
png_write_image(png_ptr, row_pointers);
png_write_end(png_ptr, info_ptr);
if (cmflag)
FREE(palette);
FREE(row_pointers);
pixDestroy(&pixt);
png_destroy_write_struct(&png_ptr, &info_ptr);
return 0;
}
/* For rgb, compose and write a row at a time */
data = pixGetData(pix);
wpl = pixGetWpl(pix);
if (d == 24) { /* See note 7 above: special case of 24 bpp rgb */
for (i = 0; i < h; i++) {
ppixel = data + i * wpl;
png_write_rows(png_ptr, (png_bytepp)&ppixel, 1);
}
} else { /* 32 bpp rgb and rgba. Write out the alpha channel if either
* the pix has 4 spp or writing it is requested anyway */
if ((rowbuffer = (png_bytep)CALLOC(w, 4)) == NULL)
return ERROR_INT("rowbuffer not made", procName, 1);
for (i = 0; i < h; i++) {
ppixel = data + i * wpl;
for (j = k = 0; j < w; j++) {
rowbuffer[k++] = GET_DATA_BYTE(ppixel, COLOR_RED);
rowbuffer[k++] = GET_DATA_BYTE(ppixel, COLOR_GREEN);
rowbuffer[k++] = GET_DATA_BYTE(ppixel, COLOR_BLUE);
if (spp == 4)
rowbuffer[k++] = GET_DATA_BYTE(ppixel, L_ALPHA_CHANNEL);
ppixel++;
}
png_write_rows(png_ptr, &rowbuffer, 1);
}
FREE(rowbuffer);
}
png_write_end(png_ptr, info_ptr);
if (cmflag)
FREE(palette);
png_destroy_write_struct(&png_ptr, &info_ptr);
return 0;
}
/*!
* pixSetZlibCompression()
*
* Input: pix
* compval (zlib compression value)
* Return: 0 if OK, 1 on error
*
* Notes:
* (1) Valid zlib compression values are in the interval [0 ... 9],
* where, as defined in zlib.h:
* 0 Z_NO_COMPRESSION
* 1 Z_BEST_SPEED (poorest compression)
* 9 Z_BEST_COMPRESSION
* For the default value, use either of these:
* 6 Z_DEFAULT_COMPRESSION
* -1 (resolves to Z_DEFAULT_COMPRESSION)
* (2) If you use the defined constants in zlib.h instead of the
* compression integers given above, you must include zlib.h.
*/
l_int32
pixSetZlibCompression(PIX *pix,
l_int32 compval)
{
PROCNAME("pixSetZlibCompression");
if (!pix)
return ERROR_INT("pix not defined", procName, 1);
if (compval < 0 || compval > 9) {
L_ERROR("Invalid zlib comp val; using default\n", procName);
compval = Z_DEFAULT_COMPRESSION;
}
pix->special = 10 + compval; /* valid range [10 ... 19] */
return 0;
}
/*---------------------------------------------------------------------*
* Setting flag for stripping 16 bits on reading *
*---------------------------------------------------------------------*/
/*!
* l_pngSetReadStrip16To8()
*
* Input: flag (1 for stripping 16 bpp to 8 bpp on reading;
* 0 for leaving 16 bpp)
* Return: void
*/
void
l_pngSetReadStrip16To8(l_int32 flag)
{
var_PNG_STRIP_16_TO_8 = flag;
}
/*---------------------------------------------------------------------*
* Read/write to memory *
*---------------------------------------------------------------------*/
#if HAVE_FMEMOPEN
extern FILE *open_memstream(char **data, size_t *size);
extern FILE *fmemopen(void *data, size_t size, const char *mode);
#endif /* HAVE_FMEMOPEN */
/*!
* pixReadMemPng()
*
* Input: cdata (const; png-encoded)
* size (of data)
* Return: pix, or null on error
*
* Notes:
* (1) The @size byte of @data must be a null character.
*/
PIX *
pixReadMemPng(const l_uint8 *cdata,
size_t size)
{
FILE *fp;
PIX *pix;
PROCNAME("pixReadMemPng");
if (!cdata)
return (PIX *)ERROR_PTR("cdata not defined", procName, NULL);
#if HAVE_FMEMOPEN
if ((fp = fmemopen((void *)cdata, size, "r")) == NULL)
return (PIX *)ERROR_PTR("stream not opened", procName, NULL);
#else
L_WARNING("work-around: writing to a temp file\n", procName);
if ((fp = tmpfile()) == NULL)
return (PIX *)ERROR_PTR("tmpfile stream not opened", procName, NULL);
fwrite(cdata, 1, size, fp);
rewind(fp);
#endif /* HAVE_FMEMOPEN */
pix = pixReadStreamPng(fp);
fclose(fp);
if (!pix) L_ERROR("pix not read\n", procName);
return pix;
}
/*!
* pixWriteMemPng()
*
* Input: &data (<return> data of tiff compressed image)
* &size (<return> size of returned data)
* pix
* gamma (use 0.0 if gamma is not defined)
* Return: 0 if OK, 1 on error
*
* Notes:
* (1) See pixWriteStreamPng() for usage. This version writes to
* memory instead of to a file stream.
*/
l_int32
pixWriteMemPng(l_uint8 **pdata,
size_t *psize,
PIX *pix,
l_float32 gamma)
{
l_int32 ret;
FILE *fp;
PROCNAME("pixWriteMemPng");
if (pdata) *pdata = NULL;
if (psize) *psize = 0;
if (!pdata)
return ERROR_INT("&data not defined", procName, 1 );
if (!psize)
return ERROR_INT("&size not defined", procName, 1 );
if (!pix)
return ERROR_INT("&pix not defined", procName, 1 );
#if HAVE_FMEMOPEN
if ((fp = open_memstream((char **)pdata, psize)) == NULL)
return ERROR_INT("stream not opened", procName, 1);
ret = pixWriteStreamPng(fp, pix, gamma);
#else
L_WARNING("work-around: writing to a temp file\n", procName);
if ((fp = tmpfile()) == NULL)
return ERROR_INT("tmpfile stream not opened", procName, 1);
ret = pixWriteStreamPng(fp, pix, gamma);
rewind(fp);
*pdata = l_binaryReadStream(fp, psize);
#endif /* HAVE_FMEMOPEN */
fclose(fp);
return ret;
}
/* --------------------------------------------*/
#endif /* HAVE_LIBPNG */
/* --------------------------------------------*/