bundles/org.eclipse.swt/Eclipse SWT/common/org/eclipse/swt/internal/image/GIFFileFormat.java - platform/eclipse.platform.swt - Git at Google

 /*******************************************************************************
  * Copyright (c) 2000, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  *     IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.swt.internal.image;


 import org.eclipse.swt.*;
 import org.eclipse.swt.graphics.*;
 import java.io.*;

 final class GIFFileFormat extends FileFormat {
 	String signature;
 	int screenWidth, screenHeight, backgroundPixel, bitsPerPixel, defaultDepth;
 	int disposalMethod = 0;
 	int delayTime = 0;
 	int transparentPixel = -1;
 	int repeatCount = 1;

 	static final int GIF_APPLICATION_EXTENSION_BLOCK_ID = 0xFF;
 	static final int GIF_GRAPHICS_CONTROL_BLOCK_ID = 0xF9;
 	static final int GIF_PLAIN_TEXT_BLOCK_ID = 0x01;
 	static final int GIF_COMMENT_BLOCK_ID = 0xFE;
 	static final int GIF_EXTENSION_BLOCK_ID = 0x21;
 	static final int GIF_IMAGE_BLOCK_ID = 0x2C;
 	static final int GIF_TRAILER_ID = 0x3B;
 	static final byte [] GIF89a = new byte[] { (byte)'G', (byte)'I', (byte)'F', (byte)'8', (byte)'9', (byte)'a' };
 	static final byte [] NETSCAPE2_0 = new byte[] { (byte)'N', (byte)'E', (byte)'T', (byte)'S', (byte)'C', (byte)'A', (byte)'P', (byte)'E', (byte)'2', (byte)'.', (byte)'0' };

 	/**
 	 * Answer a palette containing numGrays
 	 * shades of gray, ranging from black to white.
 	 */
 	static PaletteData grayRamp(int numGrays) {
 		int n = numGrays - 1;
 		RGB[] colors = new RGB[numGrays];
 		for (int i = 0; i < numGrays; i++) {
 			int intensity = (byte)((i * 3) * 256 / n);
 			colors[i] = new RGB(intensity, intensity, intensity);
 		}
 		return new PaletteData(colors);
 	}

 	boolean isFileFormat(LEDataInputStream stream) {
 		try {
 			byte[] signature = new byte[3];
 			stream.read(signature);
 			stream.unread(signature);
 			return new String(signature).equals("GIF"); //$NON-NLS-1$
 		} catch (Exception e) {
 			return false;
 		}
 	}

 	/**
 	 * Load the GIF image(s) stored in the input stream.
 	 * Return an array of ImageData representing the image(s).
 	 */
 	ImageData[] loadFromByteStream() {
 		byte[] signatureBytes = new byte[3];
 		byte[] versionBytes = new byte[3];
 		byte[] block = new byte[7];
 		try {
 			inputStream.read(signatureBytes);
 			signature = new String(signatureBytes);
 			if (!signature.equals("GIF")) //$NON-NLS-1$
 				SWT.error(SWT.ERROR_INVALID_IMAGE);

 			inputStream.read(versionBytes);

 			inputStream.read(block);
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}
 		screenWidth = (block[0] & 0xFF) | ((block[1] & 0xFF) << 8);
 		loader.logicalScreenWidth = screenWidth;
 		screenHeight = (block[2] & 0xFF) | ((block[3] & 0xFF) << 8);
 		loader.logicalScreenHeight = screenHeight;
 		byte bitField = block[4];
 		backgroundPixel = block[5] & 0xFF;
 		//aspect = block[6] & 0xFF;
 		bitsPerPixel = ((bitField >> 4) & 0x07) + 1;
 		defaultDepth = (bitField & 0x7) + 1;
 		PaletteData palette = null;
 		if ((bitField & 0x80) != 0) {
 			// Global palette.
 			//sorted = (bitField & 0x8) != 0;
 			palette = readPalette(1 << defaultDepth);
 		} else {
 			// No global palette.
 			//sorted = false;
 			backgroundPixel = -1;
 			defaultDepth = bitsPerPixel;
 		}
 		loader.backgroundPixel = backgroundPixel;

 		getExtensions();
 		int id = readID();
 		ImageData[] images = new ImageData[0];
 		while (id == GIF_IMAGE_BLOCK_ID) {
 			ImageData image = readImageBlock(palette);
 			if (loader.hasListeners()) {
 				loader.notifyListeners(new ImageLoaderEvent(loader, image, 3, true));
 			}
 			ImageData[] oldImages = images;
 			images = new ImageData[oldImages.length + 1];
 			System.arraycopy(oldImages, 0, images, 0, oldImages.length);
 			images[images.length - 1] = image;
 			try {
 				/* Read the 0-byte terminator at the end of the image. */
 				id = inputStream.read();
 				if (id > 0) {
 					/* We read the terminator earlier. */
 					inputStream.unread(new byte[] {(byte)id});
 				}
 			} catch (IOException e) {
 				SWT.error(SWT.ERROR_IO, e);
 			}
 			getExtensions();
 			id = readID();
 		}
 		return images;
 	}

 	/**
 	 * Read and return the next block or extension identifier from the file.
 	 */
 	int readID() {
 		try {
 			return inputStream.read();
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}
 		return -1;
 	}

 	/**
 	 * Read extensions until an image descriptor appears.
 	 * In the future, if we care about the extensions, they
 	 * should be properly grouped with the image data before
 	 * which they appeared. Right now, the interesting parts
 	 * of some extensions are kept, but the rest is discarded.
 	 * Throw an error if an error occurs.
 	 */
 	void getExtensions() {
 		int id = readID();
 		while (id != GIF_IMAGE_BLOCK_ID && id != GIF_TRAILER_ID && id > 0) {
 			if (id == GIF_EXTENSION_BLOCK_ID) {
 				readExtension();
 			} else {
 				SWT.error(SWT.ERROR_INVALID_IMAGE);
 			}
 			id = readID();
 		}
 		if (id == GIF_IMAGE_BLOCK_ID || id == GIF_TRAILER_ID) {
 			try {
 				inputStream.unread(new byte[] {(byte)id});
 			} catch (IOException e) {
 				SWT.error(SWT.ERROR_IO, e);
 			}
 		}
 	}

 	/**
 	 * Read a control extension.
 	 * Return the extension block data.
 	 */
 	byte[] readExtension() {
 		int extensionID = readID();
 		if (extensionID == GIF_COMMENT_BLOCK_ID)
 			return readCommentExtension();
 		if (extensionID == GIF_PLAIN_TEXT_BLOCK_ID)
 			return readPlainTextExtension();
 		if (extensionID == GIF_GRAPHICS_CONTROL_BLOCK_ID)
 			return readGraphicsControlExtension();
 		if (extensionID == GIF_APPLICATION_EXTENSION_BLOCK_ID)
 			return readApplicationExtension();
 		// Otherwise, we don't recognize the block. If the
 		// field size is correct, we can just skip over
 		// the block contents.
 		try {
 			int extSize = inputStream.read();
 			if (extSize < 0) {
 				SWT.error(SWT.ERROR_INVALID_IMAGE);
 			}
 			byte[] ext = new byte[extSize];
 			inputStream.read(ext, 0, extSize);
 			return ext;
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 			return null;
 		}
 	}

 	/**
 	 * We have just read the Comment extension identifier
 	 * from the input stream. Read in the rest of the comment
 	 * and return it. GIF comment blocks are variable size.
 	 */
 	byte[] readCommentExtension() {
 		try {
 			byte[] comment = new byte[0];
 			byte[] block = new byte[255];
 			int size = inputStream.read();
 			while ((size > 0) && (inputStream.read(block, 0, size) != -1)) {
 				byte[] oldComment = comment;
 				comment = new byte[oldComment.length + size];
 				System.arraycopy(oldComment, 0, comment, 0, oldComment.length);
 				System.arraycopy(block, 0, comment, oldComment.length, size);
 				size = inputStream.read();
 			}
 			return comment;
 		} catch (Exception e) {
 			SWT.error(SWT.ERROR_IO, e);
 			return null;
 		}
 	}

 	/**
 	 * We have just read the PlainText extension identifier
 	 * from the input stream. Read in the plain text info and text,
 	 * and return the text. GIF plain text blocks are variable size.
 	 */
 	byte[] readPlainTextExtension() {
 		try {
 			// Read size of block = 0x0C.
 			inputStream.read();
 			// Read the text information (x, y, width, height, colors).
 			byte[] info = new byte[12];
 			inputStream.read(info);
 			// Read the text.
 			byte[] text = new byte[0];
 			byte[] block = new byte[255];
 			int size = inputStream.read();
 			while ((size > 0) && (inputStream.read(block, 0, size) != -1)) {
 				byte[] oldText = text;
 				text = new byte[oldText.length + size];
 				System.arraycopy(oldText, 0, text, 0, oldText.length);
 				System.arraycopy(block, 0, text, oldText.length, size);
 				size = inputStream.read();
 			}
 			return text;
 		} catch (Exception e) {
 			SWT.error(SWT.ERROR_IO, e);
 			return null;
 		}
 	}

 	/**
 	 * We have just read the GraphicsControl extension identifier
 	 * from the input stream. Read in the control information, store
 	 * it, and return it.
 	 */
 	byte[] readGraphicsControlExtension() {
 		try {
 			// Read size of block = 0x04.
 			inputStream.read();
 			// Read the control block.
 			byte[] controlBlock = new byte[4];
 			inputStream.read(controlBlock);
 			byte bitField = controlBlock[0];
 			// Store the user input field.
 			//userInput = (bitField & 0x02) != 0;
 			// Store the disposal method.
 			disposalMethod = (bitField >> 2) & 0x07;
 			// Store the delay time.
 			delayTime = (controlBlock[1] & 0xFF) | ((controlBlock[2] & 0xFF) << 8);
 			// Store the transparent color.
 			if ((bitField & 0x01) != 0) {
 				transparentPixel = controlBlock[3] & 0xFF;
 			} else {
 				transparentPixel = -1;
 			}
 			// Read block terminator.
 			inputStream.read();
 			return controlBlock;
 		} catch (Exception e) {
 			SWT.error(SWT.ERROR_IO, e);
 			return null;
 		}
 	}

 	/**
 	 * We have just read the Application extension identifier
 	 * from the input stream.  Read in the rest of the extension,
 	 * look for and store 'number of repeats', and return the data.
 	 */
 	byte[] readApplicationExtension() {
 		try {
 			// Read size of block = 0x0B.
 			inputStream.read();
 			// Read application identifier.
 			byte[] applicationBytes = new byte[8];
 			inputStream.read(applicationBytes);
 			String application = new String(applicationBytes);
 			// Read authentication code.
 			byte[] authenticationBytes = new byte[3];
 			inputStream.read(authenticationBytes);
 			String authentication = new String(authenticationBytes);
 			// Read application data.
 			byte[] data = new byte[0];
 			byte[] block = new byte[255];
 			int size = inputStream.read();
 			while ((size > 0) && (inputStream.read(block, 0, size) != -1)) {
 				byte[] oldData = data;
 				data = new byte[oldData.length + size];
 				System.arraycopy(oldData, 0, data, 0, oldData.length);
 				System.arraycopy(block, 0, data, oldData.length, size);
 				size = inputStream.read();
 			}
 			// Look for the NETSCAPE 'repeat count' field for an animated GIF.
 			if (application.equals("NETSCAPE") && authentication.equals("2.0") && data[0] == 01) { //$NON-NLS-1$ //$NON-NLS-2$
 				repeatCount = (data[1] & 0xFF) | ((data[2] & 0xFF) << 8);
 				loader.repeatCount = repeatCount;
 			}
 			return data;
 		} catch (Exception e) {
 			SWT.error(SWT.ERROR_IO, e);
 			return null;
 		}
 	}

 	/**
 	 * Return a DeviceIndependentImage representing the
 	 * image block at the current position in the input stream.
 	 * Throw an error if an error occurs.
 	 */
 	ImageData readImageBlock(PaletteData defaultPalette) {
 		int depth;
 		PaletteData palette;
 		byte[] block = new byte[9];
 		try {
 			inputStream.read(block);
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}
 		int left = (block[0] & 0xFF) | ((block[1] & 0xFF) << 8);
 		int top = (block[2] & 0xFF) | ((block[3] & 0xFF) << 8);
 		int width = (block[4] & 0xFF) | ((block[5] & 0xFF) << 8);
 		int height = (block[6] & 0xFF) | ((block[7] & 0xFF) << 8);
 		byte bitField = block[8];
 		boolean interlaced = (bitField & 0x40) != 0;
 		//boolean sorted = (bitField & 0x20) != 0;
 		if ((bitField & 0x80) != 0) {
 			// Local palette.
 			depth = (bitField & 0x7) + 1;
 			palette = readPalette(1 << depth);
 		} else {
 			// No local palette.
 			depth = defaultDepth;
 			palette = defaultPalette;
 		}
 		/* Work around: Ignore the case where a GIF specifies an
 		 * invalid index for the transparent pixel that is larger
 		 * than the number of entries in the palette. */
 		if (transparentPixel > 1 << depth) {
 			transparentPixel = -1;
 		}
 		// Promote depth to next highest supported value.
 		if (!(depth == 1 || depth == 4 || depth == 8)) {
 			if (depth < 4)
 				depth = 4;
 			else
 				depth = 8;
 		}
 		if (palette == null) {
 			palette = grayRamp(1 << depth);
 		}
 		int initialCodeSize = -1;
 		try {
 			initialCodeSize = inputStream.read();
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}
 		if (initialCodeSize < 0) {
 			SWT.error(SWT.ERROR_INVALID_IMAGE);
 		}
 		ImageData image = ImageData.internal_new(
 			width,
 			height,
 			depth,
 			palette,
 			4,
 			null,
 			0,
 			null,
 			null,
 			-1,
 			transparentPixel,
 			SWT.IMAGE_GIF,
 			left,
 			top,
 			disposalMethod,
 			delayTime);
 		LZWCodec codec = new LZWCodec();
 		codec.decode(inputStream, loader, image, interlaced, initialCodeSize);
 		return image;
 	}

 	/**
 	 * Read a palette from the input stream.
 	 */
 	PaletteData readPalette(int numColors) {
 		byte[] bytes = new byte[numColors * 3];
 		try {
 			if (inputStream.read(bytes) != bytes.length)
 				SWT.error(SWT.ERROR_INVALID_IMAGE);
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}
 		RGB[] colors = new RGB[numColors];
 		for (int i = 0; i < numColors; i++)
 			colors[i] = new RGB(bytes[i*3] & 0xFF,
 				bytes[i*3+1] & 0xFF, bytes[i*3+2] & 0xFF);
 		return new PaletteData(colors);
 	}

 	void unloadIntoByteStream(ImageLoader loader) {

  		/* Step 1: Acquire GIF parameters. */
 		ImageData[] data = loader.data;
 		int frameCount = data.length;
 		boolean multi = frameCount > 1;
 		ImageData firstImage = data[0];
 		int logicalScreenWidth = multi ? loader.logicalScreenWidth : firstImage.width;
 		int logicalScreenHeight = multi ? loader.logicalScreenHeight : firstImage.height;
 		int backgroundPixel = loader.backgroundPixel;
 		int depth = firstImage.depth;
 		PaletteData palette = firstImage.palette;
 		RGB[] colors = palette.getRGBs();
 		short globalTable = 1;

 		/* Step 2: Check for validity and global/local color map. */
 		if (!(depth == 1 || depth == 4 || depth == 8)) {
 			SWT.error(SWT.ERROR_UNSUPPORTED_DEPTH);
 		}
 		for (int i=0; i<frameCount; i++) {
 			if (data[i].palette.isDirect) {
 				SWT.error(SWT.ERROR_INVALID_IMAGE);
 			}
 			if (multi) {
 				if (!(data[i].height <= logicalScreenHeight && data[i].width <= logicalScreenWidth && data[i].depth == depth)) {
 					SWT.error(SWT.ERROR_INVALID_IMAGE);
 				}
 				if (globalTable == 1) {
 					RGB rgbs[] = data[i].palette.getRGBs();
 					if (rgbs.length != colors.length) {
 						globalTable = 0;
 					} else {
 						for (int j=0; j<colors.length; j++) {
 							if (!(rgbs[j].red == colors[j].red &&
 								rgbs[j].green == colors[j].green &&
 								rgbs[j].blue == colors[j].blue))
 									globalTable = 0;
 						}
 					}
 				}
 			}
 		}

 		try {
  			/* Step 3: Write the GIF89a Header and Logical Screen Descriptor. */
 			outputStream.write(GIF89a);
 			int bitField = globalTable*128 + (depth-1)*16 + depth-1;
 			outputStream.writeShort((short)logicalScreenWidth);
 			outputStream.writeShort((short)logicalScreenHeight);
 			outputStream.write(bitField);
 			outputStream.write(backgroundPixel);
 			outputStream.write(0); // Aspect ratio is 1:1
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}

 		/* Step 4: Write Global Color Table if applicable. */
 		if (globalTable == 1) {
 			writePalette(palette, depth);
 		}

 		/* Step 5: Write Application Extension if applicable. */
 		if (multi) {
 			int repeatCount = loader.repeatCount;
 			try {
 				outputStream.write(GIF_EXTENSION_BLOCK_ID);
 				outputStream.write(GIF_APPLICATION_EXTENSION_BLOCK_ID);
 				outputStream.write(NETSCAPE2_0.length);
 				outputStream.write(NETSCAPE2_0);
 				outputStream.write(3); // Three bytes follow
 				outputStream.write(1); // Extension type
 				outputStream.writeShort((short) repeatCount);
 				outputStream.write(0); // Block terminator
 			} catch (IOException e) {
 				SWT.error(SWT.ERROR_IO, e);
 			}
 		}

 		for (int frame=0; frame<frameCount; frame++) {

 			/* Step 6: Write Graphics Control Block for each frame if applicable. */
 			if (multi || data[frame].transparentPixel != -1) {
 				writeGraphicsControlBlock(data[frame]);
 			}

 			/* Step 7: Write Image Header for each frame. */
 			int x = data[frame].x;
 			int y = data[frame].y;
 			int width = data[frame].width;
 			int height = data[frame].height;
 			try {
 				outputStream.write(GIF_IMAGE_BLOCK_ID);
 				byte[] block = new byte[9];
 				block[0] = (byte)(x & 0xFF);
 				block[1] = (byte)((x >> 8) & 0xFF);
 				block[2] = (byte)(y & 0xFF);
 				block[3] = (byte)((y >> 8) & 0xFF);
 				block[4] = (byte)(width & 0xFF);
 				block[5] = (byte)((width >> 8) & 0xFF);
 				block[6] = (byte)(height & 0xFF);
 				block[7] = (byte)((height >> 8) & 0xFF);
 				block[8] = (byte)(globalTable == 0 ? (depth-1) | 0x80 : 0x00);
 				outputStream.write(block);
 			} catch (IOException e) {
 				SWT.error(SWT.ERROR_IO, e);
 			}

 			/* Step 8: Write Local Color Table for each frame if applicable. */
 			if (globalTable == 0) {
 				writePalette(data[frame].palette, depth);
 			}

 			/* Step 9: Write the actual data for each frame. */
 			try {
 				outputStream.write(depth); // Minimum LZW Code size
 			} catch (IOException e) {
 				SWT.error(SWT.ERROR_IO, e);
 			}
 			new LZWCodec().encode(outputStream, data[frame]);
 		}

 		/* Step 10: Write GIF terminator. */
 		try {
 			outputStream.write(0x3B);
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}
 	}

 	/**
 	 * Write out a GraphicsControlBlock to describe
 	 * the specified device independent image.
 	 */
 	void writeGraphicsControlBlock(ImageData image) {
 		try {
 			outputStream.write(GIF_EXTENSION_BLOCK_ID);
 			outputStream.write(GIF_GRAPHICS_CONTROL_BLOCK_ID);
 			byte[] gcBlock = new byte[4];
 			gcBlock[0] = 0;
 			gcBlock[1] = 0;
 			gcBlock[2] = 0;
 			gcBlock[3] = 0;
 			if (image.transparentPixel != -1) {
 				gcBlock[0] = (byte)0x01;
 				gcBlock[3] = (byte)image.transparentPixel;
 			}
 			if (image.disposalMethod != 0) {
 				gcBlock[0] |= (byte)((image.disposalMethod & 0x07) << 2);
 			}
 			if (image.delayTime != 0) {
 				gcBlock[1] = (byte)(image.delayTime & 0xFF);
 				gcBlock[2] = (byte)((image.delayTime >> 8) & 0xFF);
 			}
 			outputStream.write((byte)gcBlock.length);
 			outputStream.write(gcBlock);
 			outputStream.write(0); // Block terminator
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}
 	}

 	/**
 	 * Write the specified palette to the output stream.
 	 */
 	void writePalette(PaletteData palette, int depth) {
 		byte[] bytes = new byte[(1 << depth) * 3];
 		int offset = 0;
 		for (int i = 0; i < palette.colors.length; i++) {
 			RGB color = palette.colors[i];
 			bytes[offset] = (byte)color.red;
 			bytes[offset + 1] = (byte)color.green;
 			bytes[offset + 2] = (byte)color.blue;
 			offset += 3;
 		}
 		try {
 			outputStream.write(bytes);
 		} catch (IOException e) {
 			SWT.error(SWT.ERROR_IO, e);
 		}
 	}
 }
	/*******************************************************************************
	* Copyright (c) 2000, 2005 IBM Corporation and others.
	* All rights reserved. This program and the accompanying materials
	* are made available under the terms of the Eclipse Public License v1.0
	* which accompanies this distribution, and is available at
	* http://www.eclipse.org/legal/epl-v10.html
	*
	* Contributors:
	* IBM Corporation - initial API and implementation
	*******************************************************************************/
	package org.eclipse.swt.internal.image;


	import org.eclipse.swt.*;
	import org.eclipse.swt.graphics.*;
	import java.io.*;

	final class GIFFileFormat extends FileFormat {
	String signature;
	int screenWidth, screenHeight, backgroundPixel, bitsPerPixel, defaultDepth;
	int disposalMethod = 0;
	int delayTime = 0;
	int transparentPixel = -1;
	int repeatCount = 1;

	static final int GIF_APPLICATION_EXTENSION_BLOCK_ID = 0xFF;
	static final int GIF_GRAPHICS_CONTROL_BLOCK_ID = 0xF9;
	static final int GIF_PLAIN_TEXT_BLOCK_ID = 0x01;
	static final int GIF_COMMENT_BLOCK_ID = 0xFE;
	static final int GIF_EXTENSION_BLOCK_ID = 0x21;
	static final int GIF_IMAGE_BLOCK_ID = 0x2C;
	static final int GIF_TRAILER_ID = 0x3B;
	static final byte [] GIF89a = new byte[] { (byte)'G', (byte)'I', (byte)'F', (byte)'8', (byte)'9', (byte)'a' };
	static final byte [] NETSCAPE2_0 = new byte[] { (byte)'N', (byte)'E', (byte)'T', (byte)'S', (byte)'C', (byte)'A', (byte)'P', (byte)'E', (byte)'2', (byte)'.', (byte)'0' };

	/**
	* Answer a palette containing numGrays
	* shades of gray, ranging from black to white.
	*/
	static PaletteData grayRamp(int numGrays) {
	int n = numGrays - 1;
	RGB[] colors = new RGB[numGrays];
	for (int i = 0; i < numGrays; i++) {
	int intensity = (byte)((i * 3) * 256 / n);
	colors[i] = new RGB(intensity, intensity, intensity);
	}
	return new PaletteData(colors);
	}

	boolean isFileFormat(LEDataInputStream stream) {
	try {
	byte[] signature = new byte[3];
	stream.read(signature);
	stream.unread(signature);
	return new String(signature).equals("GIF"); //$NON-NLS-1$
	} catch (Exception e) {
	return false;
	}
	}

	/**
	* Load the GIF image(s) stored in the input stream.
	* Return an array of ImageData representing the image(s).
	*/
	ImageData[] loadFromByteStream() {
	byte[] signatureBytes = new byte[3];
	byte[] versionBytes = new byte[3];
	byte[] block = new byte[7];
	try {
	inputStream.read(signatureBytes);
	signature = new String(signatureBytes);
	if (!signature.equals("GIF")) //$NON-NLS-1$
	SWT.error(SWT.ERROR_INVALID_IMAGE);

	inputStream.read(versionBytes);

	inputStream.read(block);
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	screenWidth = (block[0] & 0xFF) \| ((block[1] & 0xFF) << 8);
	loader.logicalScreenWidth = screenWidth;
	screenHeight = (block[2] & 0xFF) \| ((block[3] & 0xFF) << 8);
	loader.logicalScreenHeight = screenHeight;
	byte bitField = block[4];
	backgroundPixel = block[5] & 0xFF;
	//aspect = block[6] & 0xFF;
	bitsPerPixel = ((bitField >> 4) & 0x07) + 1;
	defaultDepth = (bitField & 0x7) + 1;
	PaletteData palette = null;
	if ((bitField & 0x80) != 0) {
	// Global palette.
	//sorted = (bitField & 0x8) != 0;
	palette = readPalette(1 << defaultDepth);
	} else {
	// No global palette.
	//sorted = false;
	backgroundPixel = -1;
	defaultDepth = bitsPerPixel;
	}
	loader.backgroundPixel = backgroundPixel;

	getExtensions();
	int id = readID();
	ImageData[] images = new ImageData[0];
	while (id == GIF_IMAGE_BLOCK_ID) {
	ImageData image = readImageBlock(palette);
	if (loader.hasListeners()) {
	loader.notifyListeners(new ImageLoaderEvent(loader, image, 3, true));
	}
	ImageData[] oldImages = images;
	images = new ImageData[oldImages.length + 1];
	System.arraycopy(oldImages, 0, images, 0, oldImages.length);
	images[images.length - 1] = image;
	try {
	/* Read the 0-byte terminator at the end of the image. */
	id = inputStream.read();
	if (id > 0) {
	/* We read the terminator earlier. */
	inputStream.unread(new byte[] {(byte)id});
	}
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	getExtensions();
	id = readID();
	}
	return images;
	}

	/**
	* Read and return the next block or extension identifier from the file.
	*/
	int readID() {
	try {
	return inputStream.read();
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	return -1;
	}

	/**
	* Read extensions until an image descriptor appears.
	* In the future, if we care about the extensions, they
	* should be properly grouped with the image data before
	* which they appeared. Right now, the interesting parts
	* of some extensions are kept, but the rest is discarded.
	* Throw an error if an error occurs.
	*/
	void getExtensions() {
	int id = readID();
	while (id != GIF_IMAGE_BLOCK_ID && id != GIF_TRAILER_ID && id > 0) {
	if (id == GIF_EXTENSION_BLOCK_ID) {
	readExtension();
	} else {
	SWT.error(SWT.ERROR_INVALID_IMAGE);
	}
	id = readID();
	}
	if (id == GIF_IMAGE_BLOCK_ID \|\| id == GIF_TRAILER_ID) {
	try {
	inputStream.unread(new byte[] {(byte)id});
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	}
	}

	/**
	* Read a control extension.
	* Return the extension block data.
	*/
	byte[] readExtension() {
	int extensionID = readID();
	if (extensionID == GIF_COMMENT_BLOCK_ID)
	return readCommentExtension();
	if (extensionID == GIF_PLAIN_TEXT_BLOCK_ID)
	return readPlainTextExtension();
	if (extensionID == GIF_GRAPHICS_CONTROL_BLOCK_ID)
	return readGraphicsControlExtension();
	if (extensionID == GIF_APPLICATION_EXTENSION_BLOCK_ID)
	return readApplicationExtension();
	// Otherwise, we don't recognize the block. If the
	// field size is correct, we can just skip over
	// the block contents.
	try {
	int extSize = inputStream.read();
	if (extSize < 0) {
	SWT.error(SWT.ERROR_INVALID_IMAGE);
	}
	byte[] ext = new byte[extSize];
	inputStream.read(ext, 0, extSize);
	return ext;
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	return null;
	}
	}

	/**
	* We have just read the Comment extension identifier
	* from the input stream. Read in the rest of the comment
	* and return it. GIF comment blocks are variable size.
	*/
	byte[] readCommentExtension() {
	try {
	byte[] comment = new byte[0];
	byte[] block = new byte[255];
	int size = inputStream.read();
	while ((size > 0) && (inputStream.read(block, 0, size) != -1)) {
	byte[] oldComment = comment;
	comment = new byte[oldComment.length + size];
	System.arraycopy(oldComment, 0, comment, 0, oldComment.length);
	System.arraycopy(block, 0, comment, oldComment.length, size);
	size = inputStream.read();
	}
	return comment;
	} catch (Exception e) {
	SWT.error(SWT.ERROR_IO, e);
	return null;
	}
	}

	/**
	* We have just read the PlainText extension identifier
	* from the input stream. Read in the plain text info and text,
	* and return the text. GIF plain text blocks are variable size.
	*/
	byte[] readPlainTextExtension() {
	try {
	// Read size of block = 0x0C.
	inputStream.read();
	// Read the text information (x, y, width, height, colors).
	byte[] info = new byte[12];
	inputStream.read(info);
	// Read the text.
	byte[] text = new byte[0];
	byte[] block = new byte[255];
	int size = inputStream.read();
	while ((size > 0) && (inputStream.read(block, 0, size) != -1)) {
	byte[] oldText = text;
	text = new byte[oldText.length + size];
	System.arraycopy(oldText, 0, text, 0, oldText.length);
	System.arraycopy(block, 0, text, oldText.length, size);
	size = inputStream.read();
	}
	return text;
	} catch (Exception e) {
	SWT.error(SWT.ERROR_IO, e);
	return null;
	}
	}

	/**
	* We have just read the GraphicsControl extension identifier
	* from the input stream. Read in the control information, store
	* it, and return it.
	*/
	byte[] readGraphicsControlExtension() {
	try {
	// Read size of block = 0x04.
	inputStream.read();
	// Read the control block.
	byte[] controlBlock = new byte[4];
	inputStream.read(controlBlock);
	byte bitField = controlBlock[0];
	// Store the user input field.
	//userInput = (bitField & 0x02) != 0;
	// Store the disposal method.
	disposalMethod = (bitField >> 2) & 0x07;
	// Store the delay time.
	delayTime = (controlBlock[1] & 0xFF) \| ((controlBlock[2] & 0xFF) << 8);
	// Store the transparent color.
	if ((bitField & 0x01) != 0) {
	transparentPixel = controlBlock[3] & 0xFF;
	} else {
	transparentPixel = -1;
	}
	// Read block terminator.
	inputStream.read();
	return controlBlock;
	} catch (Exception e) {
	SWT.error(SWT.ERROR_IO, e);
	return null;
	}
	}

	/**
	* We have just read the Application extension identifier
	* from the input stream. Read in the rest of the extension,
	* look for and store 'number of repeats', and return the data.
	*/
	byte[] readApplicationExtension() {
	try {
	// Read size of block = 0x0B.
	inputStream.read();
	// Read application identifier.
	byte[] applicationBytes = new byte[8];
	inputStream.read(applicationBytes);
	String application = new String(applicationBytes);
	// Read authentication code.
	byte[] authenticationBytes = new byte[3];
	inputStream.read(authenticationBytes);
	String authentication = new String(authenticationBytes);
	// Read application data.
	byte[] data = new byte[0];
	byte[] block = new byte[255];
	int size = inputStream.read();
	while ((size > 0) && (inputStream.read(block, 0, size) != -1)) {
	byte[] oldData = data;
	data = new byte[oldData.length + size];
	System.arraycopy(oldData, 0, data, 0, oldData.length);
	System.arraycopy(block, 0, data, oldData.length, size);
	size = inputStream.read();
	}
	// Look for the NETSCAPE 'repeat count' field for an animated GIF.
	if (application.equals("NETSCAPE") && authentication.equals("2.0") && data[0] == 01) { //$NON-NLS-1$ //$NON-NLS-2$
	repeatCount = (data[1] & 0xFF) \| ((data[2] & 0xFF) << 8);
	loader.repeatCount = repeatCount;
	}
	return data;
	} catch (Exception e) {
	SWT.error(SWT.ERROR_IO, e);
	return null;
	}
	}

	/**
	* Return a DeviceIndependentImage representing the
	* image block at the current position in the input stream.
	* Throw an error if an error occurs.
	*/
	ImageData readImageBlock(PaletteData defaultPalette) {
	int depth;
	PaletteData palette;
	byte[] block = new byte[9];
	try {
	inputStream.read(block);
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	int left = (block[0] & 0xFF) \| ((block[1] & 0xFF) << 8);
	int top = (block[2] & 0xFF) \| ((block[3] & 0xFF) << 8);
	int width = (block[4] & 0xFF) \| ((block[5] & 0xFF) << 8);
	int height = (block[6] & 0xFF) \| ((block[7] & 0xFF) << 8);
	byte bitField = block[8];
	boolean interlaced = (bitField & 0x40) != 0;
	//boolean sorted = (bitField & 0x20) != 0;
	if ((bitField & 0x80) != 0) {
	// Local palette.
	depth = (bitField & 0x7) + 1;
	palette = readPalette(1 << depth);
	} else {
	// No local palette.
	depth = defaultDepth;
	palette = defaultPalette;
	}
	/* Work around: Ignore the case where a GIF specifies an
	* invalid index for the transparent pixel that is larger
	* than the number of entries in the palette. */
	if (transparentPixel > 1 << depth) {
	transparentPixel = -1;
	}
	// Promote depth to next highest supported value.
	if (!(depth == 1 \|\| depth == 4 \|\| depth == 8)) {
	if (depth < 4)
	depth = 4;
	else
	depth = 8;
	}
	if (palette == null) {
	palette = grayRamp(1 << depth);
	}
	int initialCodeSize = -1;
	try {
	initialCodeSize = inputStream.read();
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	if (initialCodeSize < 0) {
	SWT.error(SWT.ERROR_INVALID_IMAGE);
	}
	ImageData image = ImageData.internal_new(
	width,
	height,
	depth,
	palette,
	4,
	null,
	0,
	null,
	null,
	-1,
	transparentPixel,
	SWT.IMAGE_GIF,
	left,
	top,
	disposalMethod,
	delayTime);
	LZWCodec codec = new LZWCodec();
	codec.decode(inputStream, loader, image, interlaced, initialCodeSize);
	return image;
	}

	/**
	* Read a palette from the input stream.
	*/
	PaletteData readPalette(int numColors) {
	byte[] bytes = new byte[numColors * 3];
	try {
	if (inputStream.read(bytes) != bytes.length)
	SWT.error(SWT.ERROR_INVALID_IMAGE);
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	RGB[] colors = new RGB[numColors];
	for (int i = 0; i < numColors; i++)
	colors[i] = new RGB(bytes[i*3] & 0xFF,
	bytes[i3+1] & 0xFF, bytes[i3+2] & 0xFF);
	return new PaletteData(colors);
	}

	void unloadIntoByteStream(ImageLoader loader) {

	/* Step 1: Acquire GIF parameters. */
	ImageData[] data = loader.data;
	int frameCount = data.length;
	boolean multi = frameCount > 1;
	ImageData firstImage = data[0];
	int logicalScreenWidth = multi ? loader.logicalScreenWidth : firstImage.width;
	int logicalScreenHeight = multi ? loader.logicalScreenHeight : firstImage.height;
	int backgroundPixel = loader.backgroundPixel;
	int depth = firstImage.depth;
	PaletteData palette = firstImage.palette;
	RGB[] colors = palette.getRGBs();
	short globalTable = 1;

	/* Step 2: Check for validity and global/local color map. */
	if (!(depth == 1 \|\| depth == 4 \|\| depth == 8)) {
	SWT.error(SWT.ERROR_UNSUPPORTED_DEPTH);
	}
	for (int i=0; i<frameCount; i++) {
	if (data[i].palette.isDirect) {
	SWT.error(SWT.ERROR_INVALID_IMAGE);
	}
	if (multi) {
	if (!(data[i].height <= logicalScreenHeight && data[i].width <= logicalScreenWidth && data[i].depth == depth)) {
	SWT.error(SWT.ERROR_INVALID_IMAGE);
	}
	if (globalTable == 1) {
	RGB rgbs[] = data[i].palette.getRGBs();
	if (rgbs.length != colors.length) {
	globalTable = 0;
	} else {
	for (int j=0; j<colors.length; j++) {
	if (!(rgbs[j].red == colors[j].red &&
	rgbs[j].green == colors[j].green &&
	rgbs[j].blue == colors[j].blue))
	globalTable = 0;
	}
	}
	}
	}
	}

	try {
	/* Step 3: Write the GIF89a Header and Logical Screen Descriptor. */
	outputStream.write(GIF89a);
	int bitField = globalTable128 + (depth-1)16 + depth-1;
	outputStream.writeShort((short)logicalScreenWidth);
	outputStream.writeShort((short)logicalScreenHeight);
	outputStream.write(bitField);
	outputStream.write(backgroundPixel);
	outputStream.write(0); // Aspect ratio is 1:1
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}

	/* Step 4: Write Global Color Table if applicable. */
	if (globalTable == 1) {
	writePalette(palette, depth);
	}

	/* Step 5: Write Application Extension if applicable. */
	if (multi) {
	int repeatCount = loader.repeatCount;
	try {
	outputStream.write(GIF_EXTENSION_BLOCK_ID);
	outputStream.write(GIF_APPLICATION_EXTENSION_BLOCK_ID);
	outputStream.write(NETSCAPE2_0.length);
	outputStream.write(NETSCAPE2_0);
	outputStream.write(3); // Three bytes follow
	outputStream.write(1); // Extension type
	outputStream.writeShort((short) repeatCount);
	outputStream.write(0); // Block terminator
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	}

	for (int frame=0; frame<frameCount; frame++) {

	/* Step 6: Write Graphics Control Block for each frame if applicable. */
	if (multi \|\| data[frame].transparentPixel != -1) {
	writeGraphicsControlBlock(data[frame]);
	}

	/* Step 7: Write Image Header for each frame. */
	int x = data[frame].x;
	int y = data[frame].y;
	int width = data[frame].width;
	int height = data[frame].height;
	try {
	outputStream.write(GIF_IMAGE_BLOCK_ID);
	byte[] block = new byte[9];
	block[0] = (byte)(x & 0xFF);
	block[1] = (byte)((x >> 8) & 0xFF);
	block[2] = (byte)(y & 0xFF);
	block[3] = (byte)((y >> 8) & 0xFF);
	block[4] = (byte)(width & 0xFF);
	block[5] = (byte)((width >> 8) & 0xFF);
	block[6] = (byte)(height & 0xFF);
	block[7] = (byte)((height >> 8) & 0xFF);
	block[8] = (byte)(globalTable == 0 ? (depth-1) \| 0x80 : 0x00);
	outputStream.write(block);
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}

	/* Step 8: Write Local Color Table for each frame if applicable. */
	if (globalTable == 0) {
	writePalette(data[frame].palette, depth);
	}

	/* Step 9: Write the actual data for each frame. */
	try {
	outputStream.write(depth); // Minimum LZW Code size
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	new LZWCodec().encode(outputStream, data[frame]);
	}

	/* Step 10: Write GIF terminator. */
	try {
	outputStream.write(0x3B);
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	}

	/**
	* Write out a GraphicsControlBlock to describe
	* the specified device independent image.
	*/
	void writeGraphicsControlBlock(ImageData image) {
	try {
	outputStream.write(GIF_EXTENSION_BLOCK_ID);
	outputStream.write(GIF_GRAPHICS_CONTROL_BLOCK_ID);
	byte[] gcBlock = new byte[4];
	gcBlock[0] = 0;
	gcBlock[1] = 0;
	gcBlock[2] = 0;
	gcBlock[3] = 0;
	if (image.transparentPixel != -1) {
	gcBlock[0] = (byte)0x01;
	gcBlock[3] = (byte)image.transparentPixel;
	}
	if (image.disposalMethod != 0) {
	gcBlock[0] \|= (byte)((image.disposalMethod & 0x07) << 2);
	}
	if (image.delayTime != 0) {
	gcBlock[1] = (byte)(image.delayTime & 0xFF);
	gcBlock[2] = (byte)((image.delayTime >> 8) & 0xFF);
	}
	outputStream.write((byte)gcBlock.length);
	outputStream.write(gcBlock);
	outputStream.write(0); // Block terminator
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	}

	/**
	* Write the specified palette to the output stream.
	*/
	void writePalette(PaletteData palette, int depth) {
	byte[] bytes = new byte[(1 << depth) * 3];
	int offset = 0;
	for (int i = 0; i < palette.colors.length; i++) {
	RGB color = palette.colors[i];
	bytes[offset] = (byte)color.red;
	bytes[offset + 1] = (byte)color.green;
	bytes[offset + 2] = (byte)color.blue;
	offset += 3;
	}
	try {
	outputStream.write(bytes);
	} catch (IOException e) {
	SWT.error(SWT.ERROR_IO, e);
	}
	}
	}