/******************************************************************************* * Copyright (c) 2000, 2003 IBM Corporation and others. * All rights reserved. This program and the accompanying materials  * are made available under the terms of the Common Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/cpl-v10.html *  * Contributors: *     IBM Corporation - initial API and implementation *******************************************************************************/package org.eclipse.swt.internal.image;import org.eclipse.swt.*;public class PngTrnsChunk extends PngChunk {	static final int TRANSPARENCY_TYPE_PIXEL = 0;	static final int TRANSPARENCY_TYPE_ALPHAS = 1;	PngTrnsChunk(byte[] reference){	super(reference);}void validateLength(PngIhdrChunk header, PngPlteChunk paletteChunk) {	boolean valid;	switch (header.getColorType()) {		case PngIhdrChunk.COLOR_TYPE_RGB:			// Three 2-byte values (RGB)			valid = getLength() == 6;			break;		case PngIhdrChunk.COLOR_TYPE_PALETTE:			// Three 2-byte values (RGB)			valid = getLength() <= paletteChunk.getLength();			break;		case PngIhdrChunk.COLOR_TYPE_GRAYSCALE:			// One 2-byte value			valid = getLength() == 2;			break;		// Cannot use both Alpha and tRNS		case PngIhdrChunk.COLOR_TYPE_RGB_WITH_ALPHA:		case PngIhdrChunk.COLOR_TYPE_GRAYSCALE_WITH_ALPHA:		default:			valid = false;	}	if (!valid) {		SWT.error(SWT.ERROR_INVALID_IMAGE);	}}/** * Answer whether the chunk is a valid tRNS chunk. */void validate(PngFileReadState readState, PngIhdrChunk headerChunk, PngPlteChunk paletteChunk) {	if (!readState.readIHDR		|| (headerChunk.getMustHavePalette() && !readState.readPLTE)		|| readState.readIDAT		|| readState.readIEND) 	{		SWT.error(SWT.ERROR_INVALID_IMAGE);	} else {		readState.readTRNS = true;	}		validateLength(headerChunk, paletteChunk);		super.validate(readState, headerChunk);}int getTransparencyType(PngIhdrChunk header) {	if (header.getColorType() == PngIhdrChunk.COLOR_TYPE_PALETTE) {		return TRANSPARENCY_TYPE_ALPHAS;	}	return TRANSPARENCY_TYPE_PIXEL;}/** * Answer the transparent pixel RGB value. * This is not valid for palette color types. * This is not valid for alpha color types. * This will convert a grayscale value into * a palette index. * It will compress a 6 byte RGB into a 3 byte * RGB. */int getSwtTransparentPixel(PngIhdrChunk header) {	switch (header.getColorType()) {		case PngIhdrChunk.COLOR_TYPE_GRAYSCALE:			int gray = ((reference[DATA_OFFSET] & 0xFF) << 8)				+ (reference[DATA_OFFSET + 1] & 0xFF);			if (header.getBitDepth() > 8) {				return PNGFileFormat.compress16BitDepthTo8BitDepth(gray);			}			return gray & 0xFF;		case PngIhdrChunk.COLOR_TYPE_RGB:			int red = ((reference[DATA_OFFSET] & 0xFF) << 8)				| (reference[DATA_OFFSET + 1] & 0xFF);			int green = ((reference[DATA_OFFSET + 2] & 0xFF) << 8)				| (reference[DATA_OFFSET + 3] & 0xFF);			int blue = ((reference[DATA_OFFSET + 4] & 0xFF) << 8)				| (reference[DATA_OFFSET + 5] & 0xFF);						if (header.getBitDepth() > 8) {				red = PNGFileFormat.compress16BitDepthTo8BitDepth(red);				green = PNGFileFormat.compress16BitDepthTo8BitDepth(green);				blue = PNGFileFormat.compress16BitDepthTo8BitDepth(blue);						}			return (red << 16) | (green << 8) | blue;			default:			SWT.error(SWT.ERROR_INVALID_IMAGE);			return -1;	}}/** * Answer an array of Alpha values that correspond to the  * colors in the palette. * This is only valid for the COLOR_TYPE_PALETTE color type. */byte[] getAlphaValues(PngIhdrChunk header, PngPlteChunk paletteChunk) {	if (header.getColorType() != PngIhdrChunk.COLOR_TYPE_PALETTE) {		SWT.error(SWT.ERROR_INVALID_IMAGE);	}	byte[] alphas = new byte[paletteChunk.getPaletteSize()];	int dataLength = getLength();	int i = 0;	for (i = 0; i < dataLength; i++) {		alphas[i] = reference[DATA_OFFSET + i];	}	/**	 * Any palette entries which do not have a corresponding	 * alpha value in the tRNS chunk are spec'd to have an 	 * alpha of 255.	 */	for (int j = i; j < alphas.length; j++) {		alphas[j] = (byte) 255;	}	return alphas;}}