pngfileformat.java

源码为Eclipse开源开发平台桌面开发工具SWT的源代码,

/*******************************************************************************
 * Copyright (c) 2000, 2004 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 java.io.*;
import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;

final class PNGFileFormat extends FileFormat {
	static final int SIGNATURE_LENGTH = 8;
	PngDecodingDataStream decodingStream;
	PngIhdrChunk headerChunk;
	PngPlteChunk paletteChunk;
	PngTrnsChunk trnsChunk;
	ImageData imageData;
	byte[] data;
	byte[] alphaPalette;

/**
 * Skip over signature data. This has already been
 * verified in isPNGFile(). 
 */
void readSignature() throws IOException {
	byte[] signature = new byte[SIGNATURE_LENGTH];
	inputStream.read(signature);
}
/**
 * Load the PNG image from the byte stream.
 */
ImageData[] loadFromByteStream() {
	try {
		readSignature();
		PngChunkReader chunkReader = new PngChunkReader(inputStream);
		headerChunk = chunkReader.getIhdrChunk();
		int imageSize = getAlignedBytesPerRow() * headerChunk.getHeight();
		data = new byte[imageSize];		
		imageData = ImageData.internal_new(
			headerChunk.getWidth(),
			headerChunk.getHeight(),
			headerChunk.getSwtBitsPerPixel(),
			new PaletteData(0, 0, 0),
			4,
			data,
			0,
			null,
			null,
			-1,
			-1,
			SWT.IMAGE_PNG,
			0,
			0,
			0,
			0);		
			
		if (headerChunk.usesDirectColor()) {
			imageData.palette = headerChunk.getPaletteData();
		}
		
		// Read and process chunks until the IEND chunk is encountered.
		while (chunkReader.hasMoreChunks()) {
			readNextChunk(chunkReader);
		}
						
		return new ImageData[] {imageData};
	} catch (IOException e) {
		SWT.error(SWT.ERROR_INVALID_IMAGE);
		return null;
	}
}
/**
 * Read and handle the next chunk of data from the 
 * PNG file.
 */
void readNextChunk(PngChunkReader chunkReader) {
	PngChunk chunk = chunkReader.readNextChunk();
	switch (chunk.getChunkType()) {
		case PngChunk.CHUNK_IEND:
			break;
		case PngChunk.CHUNK_PLTE:
			if (!headerChunk.usesDirectColor()) {
				paletteChunk = (PngPlteChunk) chunk;
				imageData.palette = paletteChunk.getPaletteData();						
			}			
			break;
		case PngChunk.CHUNK_tRNS:
			PngTrnsChunk trnsChunk = (PngTrnsChunk) chunk;
			if (trnsChunk.getTransparencyType(headerChunk) == 
				PngTrnsChunk.TRANSPARENCY_TYPE_PIXEL) 
			{
				imageData.transparentPixel = 
					trnsChunk.getSwtTransparentPixel(headerChunk);
			} else {
				alphaPalette = trnsChunk.getAlphaValues(headerChunk, paletteChunk);
				int transparentCount = 0, transparentPixel = -1;
				for (int i = 0; i < alphaPalette.length; i++) {
					if ((alphaPalette[i] & 0xFF) != 255) {
						transparentCount++;
						transparentPixel = i;
					}
				}
				if (transparentCount == 0) {
					alphaPalette = null;
				} else if (transparentCount == 1 && alphaPalette[transparentPixel] == 0) {
					alphaPalette = null;
					imageData.transparentPixel = transparentPixel;
				}
			}
			break;
		case PngChunk.CHUNK_IDAT:
			if (chunkReader.readPixelData()) {
				// All IDAT chunks in an image file must be
				// sequential. If the pixel data has already
				// been read and another IDAT block is encountered,
				// then this is an invalid image.
				SWT.error(SWT.ERROR_INVALID_IMAGE);
			} else {
				// Read in the pixel data for the image. This should
				// go through all the image's IDAT chunks. 	
				PngIdatChunk dataChunk = (PngIdatChunk) chunk;
				readPixelData(dataChunk, chunkReader);				
			}
			break;
		default:
			if (chunk.isCritical()) {
				// All critical chunks must be supported.
				SWT.error(SWT.ERROR_NOT_IMPLEMENTED);
			}
	}
}
void unloadIntoByteStream(ImageData p1) {
	SWT.error(SWT.ERROR_NOT_IMPLEMENTED);
}
boolean isFileFormat(LEDataInputStream stream) {
	try {
		byte[] signature = new byte[SIGNATURE_LENGTH];
		stream.read(signature);
		stream.unread(signature);
		if ((signature[0] & 0xFF) != 137) return false; //137
		if ((signature[1] & 0xFF) != 80) return false; //P
		if ((signature[2] & 0xFF) != 78) return false; //N
		if ((signature[3] & 0xFF) != 71) return false; //G
		if ((signature[4] & 0xFF) != 13) return false; //<RETURN>
		if ((signature[5] & 0xFF) != 10) return false; //<LINEFEED>
		if ((signature[6] & 0xFF) != 26) return false; //<CTRL/Z>
		if ((signature[7] & 0xFF) != 10) return false; //<LINEFEED>		
		return true;
	} catch (Exception e) {
		return false;
	}
}
/**
 * SWT does not support 16-bit depths. If this image uses
 * 16-bit depths, convert the data to an 8-bit depth.
 */
byte[] validateBitDepth(byte[] data) {
	if (headerChunk.getBitDepth() > 8) {
		byte[] result = new byte[data.length / 2];
		compress16BitDepthTo8BitDepth(data, 0, result, 0, result.length);
		return result;
	} else {
		return data;
	}
}
/**
 * SWT does not support greyscale as a color type. For
 * plain grayscale, we create a palette. For Grayscale
 * with Alpha, however, we need to convert the pixels
 * to use RGB values.
 * Note: This method assumes that the bit depth of the
 * data has already been restricted to 8 or less.
 */
void setPixelData(byte[] data, ImageData imageData) {
	switch (headerChunk.getColorType()) {
		case PngIhdrChunk.COLOR_TYPE_GRAYSCALE_WITH_ALPHA:
		{
			int width = imageData.width;
			int height = imageData.height;
			int destBytesPerLine = imageData.bytesPerLine;
			/*
			* If the image uses 16-bit depth, it is converted
			* to an 8-bit depth image.
			*/
			int srcBytesPerLine = getAlignedBytesPerRow();
			if (headerChunk.getBitDepth() > 8) srcBytesPerLine /= 2;

			byte[] rgbData = new byte[destBytesPerLine * height];
			byte[] alphaData = new byte[width * height];
			for (int y = 0; y < height; y++) {
				int srcIndex = srcBytesPerLine * y;
				int destIndex = destBytesPerLine * y;
				int destAlphaIndex = width * y;
				for (int x = 0; x < width; x++) {
					byte grey = data[srcIndex];
					byte alpha = data[srcIndex + 1];
					rgbData[destIndex + 0] = grey;
					rgbData[destIndex + 1] = grey;
					rgbData[destIndex + 2] = grey;
					alphaData[destAlphaIndex] = alpha;
					srcIndex += 2;
					destIndex += 3;
					destAlphaIndex++;
				}
			}
			imageData.data = rgbData;
			imageData.alphaData = alphaData;
			break;
		}
		case PngIhdrChunk.COLOR_TYPE_RGB_WITH_ALPHA:
		{
			int width = imageData.width;
			int height = imageData.height;
			int destBytesPerLine = imageData.bytesPerLine;
			int srcBytesPerLine = getAlignedBytesPerRow();
			/*
			* If the image uses 16-bit depth, it is converted
			* to an 8-bit depth image.
			*/
			if (headerChunk.getBitDepth() > 8) srcBytesPerLine /= 2;

			byte[] rgbData = new byte[destBytesPerLine * height];
			byte[] alphaData = new byte[width * height];
			for (int y = 0; y < height; y++) {
				int srcIndex = srcBytesPerLine * y;
				int destIndex = destBytesPerLine * y;
				int destAlphaIndex = width * y;
				for (int x = 0; x < width; x++) {
					rgbData[destIndex + 0] = data[srcIndex + 0];
					rgbData[destIndex + 1] = data[srcIndex + 1];
					rgbData[destIndex + 2] = data[srcIndex + 2];
					alphaData[destAlphaIndex] = data[srcIndex + 3];
					srcIndex += 4;
					destIndex += 3;
					destAlphaIndex++;
				}
			}
			imageData.data = rgbData;
			imageData.alphaData = alphaData;
			break;
		}		
		case PngIhdrChunk.COLOR_TYPE_RGB:
			imageData.data = data;
			break;
		case PngIhdrChunk.COLOR_TYPE_PALETTE:
			imageData.data = data;
			if (alphaPalette != null) {
				int size = imageData.width * imageData.height;
				byte[] alphaData = new byte[size];
				byte[] pixelData = new byte[size];
				imageData.getPixels(0, 0, size, pixelData, 0);
				for (int i = 0; i < pixelData.length; i++) {
					alphaData[i] = alphaPalette[pixelData[i] & 0xFF];
				}
				imageData.alphaData = alphaData;
			}
			break;
		default:
			imageData.data = data;
			break;
	}
}
/**
 * PNG supports some color types and bit depths that are 
 * unsupported by SWT. If the image uses an unsupported
 * color type (either of the gray scale types) or bit
 * depth (16), convert the data to an SWT-supported
 * format. Then assign the data into the ImageData given.
 */