ngryman/ribs

/*!
 * ribs
 * Copyright (c) 2013-2014 Nicolas Gryman <ngryman@gmail.com>
 * LGPL Licensed
 */

#include "decode.h"
#include "../image.h"

using namespace std;
using namespace v8;
using namespace node;
using namespace ribs;

static string Format(pixel_t* data);

OPERATION_PREPARE(Decode, {
    // check against mandatory buffer input
    if (!Buffer::HasInstance(args[0])) throw "invalid input buffer";

    // convert the node buffer to an OCV matrix.
    // we do this because OCV only accepts matrix as input for imdecode.
    // however this should not have any performance input as the matrix does not copy data.
    auto buffer = reinterpret_cast<pixel_t*>(Buffer::Data(args[0]->ToObject()));
    auto length = Buffer::Length(args[0]->ToObject());

    // store input format
    inFormat = Format(buffer);

    inMat = cv::Mat(length, 1, CV_8UC1, buffer);
})

OPERATION_CLEANUP(Decode, {})

OPERATION_PROCESS(Decode, {
    try {
        // decode
        outMat = cv::Mat(cv::imdecode(inMat, CV_LOAD_IMAGE_UNCHANGED));
    }
    catch (...) {
        // OCV uses assertion to handle errors, thus the message is not very explicit.
        // we simply do nothing and check against outMat.
    }

    // empty matrix, set error
    if (outMat.empty()) {
        error = "operation error: decode";
    }
})

OPERATION_VALUE(Decode, {
    return Image::New(outMat, inFormat);
})

string Format(pixel_t* data) {
    // jpeg
    if (0xff == data[0] && 0xd8 == data[1])
        return "jpg";

    // png
    if ('P' == data[1] && 'N' == data[2] && 'G' == data[3])
        return "png";

    // gif
    if ('G' == data[0] && 'I' == data[1] && 'F' == data[2])
        return "gif";

    // tiff
    // 42 in little/big endian, funky
    if (('M' == data[0] && 'M' == data[1]) ||
        ('I' == data[0] && 'I' == data[1]))
        return "tiff";

    // bmp
    if (('B' == data[0] && 'M' == data[1]) ||
        ('B' == data[0] && 'A' == data[1]) ||
        ('C' == data[0] && 'I' == data[1]) ||
        ('C' == data[0] && 'P' == data[1]) ||
        ('I' == data[0] && 'C' == data[1]) ||
        ('P' == data[0] && 'T' == data[1]))
            return "bmp";

    return "";
}