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/*
* 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.
*/
package 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)
*/
public abstract class LuminanceSource {
private final int width;
private final int height;
protected LuminanceSource(int width, int height) {
this.width = width;
this.height = height;
}
/**
* 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, 0 <= y < 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 byte[] getRow(int y, byte[] row);
/**
* Fetches luminance data for the underlying bitmap. Values should be fetched using:
* 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 byte[] getMatrix();
/**
* @return The width of the bitmap.
*/
public final int getWidth() {
return width;
}
/**
* @return The height of the bitmap.
*/
public final int getHeight() {
return height;
}
/**
* @return Whether this subclass supports cropping.
*/
public boolean isCropSupported() {
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, 0 <= left < getWidth().
* @param top The top coordinate, 0 <= top <= 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 LuminanceSource crop(int left, int top, int width, int height) {
throw new RuntimeException("This luminance source does not support cropping.");
}
/**
* @return Whether this subclass supports counter-clockwise rotation.
*/
public boolean isRotateSupported() {
return false;
}
/**
* Returns a new object with rotated image data. Only callable if isRotateSupported() is true.
*
* @return A rotated version of this object.
*/
public LuminanceSource rotateCounterClockwise() {
throw new RuntimeException("This luminance source does not support rotation.");
}
}
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