src/core/LuminanceSource.ts
/*
* Copyright 2009 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import StringBuilder from './util/StringBuilder';
import UnsupportedOperationException from './UnsupportedOperationException';
/*namespace com.google.zxing {*/
/**
* The purpose of this class hierarchy is to abstract different bitmap implementations across
* platforms into a standard interface for requesting greyscale luminance values. The interface
* only provides immutable methods; therefore crop and rotation create copies. This is to ensure
* that one Reader does not modify the original luminance source and leave it in an unknown state
* for other Readers in the chain.
*
* @author dswitkin@google.com (Daniel Switkin)
*/
abstract class LuminanceSource {
protected constructor(private width: number /*int*/, private height: number /*int*/) { }
/**
* Fetches one row of luminance data from the underlying platform's bitmap. Values range from
* 0 (black) to 255 (white). Because Java does not have an unsigned byte type, callers will have
* to bitwise and with 0xff for each value. It is preferable for implementations of this method
* to only fetch this row rather than the whole image, since no 2D Readers may be installed and
* getMatrix() may never be called.
*
* @param y The row to fetch, which must be in [0,getHeight())
* @param row An optional preallocated array. If null or too small, it will be ignored.
* Always use the returned object, and ignore the .length of the array.
* @return An array containing the luminance data.
*/
public abstract getRow(y: number /*int*/, row?: Uint8ClampedArray): Uint8ClampedArray;
/**
* Fetches luminance data for the underlying bitmap. Values should be fetched using:
* {@code int luminance = array[y * width + x] & 0xff}
*
* @return A row-major 2D array of luminance values. Do not use result.length as it may be
* larger than width * height bytes on some platforms. Do not modify the contents
* of the result.
*/
public abstract getMatrix(): Uint8ClampedArray;
/**
* @return The width of the bitmap.
*/
public getWidth(): number /*int*/ {
return this.width;
}
/**
* @return The height of the bitmap.
*/
public getHeight(): number /*int*/ {
return this.height;
}
/**
* @return Whether this subclass supports cropping.
*/
public isCropSupported(): boolean {
return false;
}
/**
* Returns a new object with cropped image data. Implementations may keep a reference to the
* original data rather than a copy. Only callable if isCropSupported() is true.
*
* @param left The left coordinate, which must be in [0,getWidth())
* @param top The top coordinate, which must be in [0,getHeight())
* @param width The width of the rectangle to crop.
* @param height The height of the rectangle to crop.
* @return A cropped version of this object.
*/
public crop(left: number /*int*/, top: number /*int*/, width: number /*int*/, height: number /*int*/): LuminanceSource {
throw new UnsupportedOperationException('This luminance source does not support cropping.');
}
/**
* @return Whether this subclass supports counter-clockwise rotation.
*/
public isRotateSupported(): boolean {
return false;
}
/**
* @return a wrapper of this {@code LuminanceSource} which inverts the luminances it returns -- black becomes
* white and vice versa, and each value becomes (255-value).
*/
public abstract invert(): LuminanceSource;
/**
* Returns a new object with rotated image data by 90 degrees counterclockwise.
* Only callable if {@link #isRotateSupported()} is true.
*
* @return A rotated version of this object.
*/
public rotateCounterClockwise(): LuminanceSource {
throw new UnsupportedOperationException('This luminance source does not support rotation by 90 degrees.');
}
/**
* Returns a new object with rotated image data by 45 degrees counterclockwise.
* Only callable if {@link #isRotateSupported()} is true.
*
* @return A rotated version of this object.
*/
public rotateCounterClockwise45(): LuminanceSource {
throw new UnsupportedOperationException('This luminance source does not support rotation by 45 degrees.');
}
/*@Override*/
public toString(): string {
const row = new Uint8ClampedArray(this.width);
let result = new StringBuilder();
for (let y = 0; y < this.height; y++) {
const sourceRow = this.getRow(y, row);
for (let x = 0; x < this.width; x++) {
const luminance = sourceRow[x] & 0xFF;
let c;
if (luminance < 0x40) {
c = '#';
} else if (luminance < 0x80) {
c = '+';
} else if (luminance < 0xC0) {
c = '.';
} else {
c = ' ';
}
result.append(c);
}
result.append('\n');
}
return result.toString();
}
}
export default LuminanceSource;