mirror of
https://github.com/fadden/6502bench.git
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359 lines
14 KiB
C#
359 lines
14 KiB
C#
/*
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* Copyright 2019 faddenSoft
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Collections.Generic;
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using System.Diagnostics;
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using System.Text;
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namespace CommonUtil {
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/// <summary>
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/// Representation of a GIF image, with the various pieces broken out.
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/// </summary>
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/// <remarks>
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/// This has only been tested with the GIF images created by the Windows Media GifEncoder,
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/// which are GIF89a with no global color table.
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///
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/// References:
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/// https://www.w3.org/Graphics/GIF/spec-gif87.txt
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/// https://www.w3.org/Graphics/GIF/spec-gif89a.txt
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/// </remarks>
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public class UnpackedGif {
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//
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// Header.
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//
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public enum FileVersion { Unknown = 0, Gif87a, Gif89a };
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private static readonly byte[] GIF87A = new byte[] {
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(byte)'G', (byte)'I', (byte)'F', (byte)'8', (byte)'7', (byte)'a'
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};
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private static readonly byte[] GIF89A = new byte[] {
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(byte)'G', (byte)'I', (byte)'F', (byte)'8', (byte)'9', (byte)'a'
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};
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public FileVersion FileVer { get; private set; }
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//
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// Logical screen descriptor.
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//
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public ushort LogicalScreenWidth { get; private set; }
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public ushort LogicalScreenHeight { get; private set; }
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public bool GlobalColorTableFlag { get; private set; }
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public byte ColorResolution { get; private set; }
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public bool SortFlag { get; private set; }
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public byte GlobalColorTableSize { get; private set; }
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public byte BackgroundColorIndex { get; private set; }
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public byte PixelAspectRatio { get; private set; }
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//
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// Global color table.
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//
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public byte[] GlobalColorTable { get; private set; }
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//
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// Extension block constants.
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//
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public const byte EXTENSION_INTRODUCER = 0x21;
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public const byte APP_EXTENSION_LABEL = 0xff;
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public const byte COMMENT_LABEL = 0xfe;
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public const byte GRAPHIC_CONTROL_LABEL = 0xf9;
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public const byte PLAIN_TEXT_LABEL = 0x01;
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//
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// Graphic control extension.
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//
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// These are optional. At most one may precede a graphic rendering block.
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//
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public class GraphicControlExtension {
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public enum DisposalMethods : byte {
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None = 0,
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DoNotDispose = 1,
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RestoreBackground = 2,
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RestorePrevious = 3
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}
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public byte DisposalMethod { get; private set; }
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public bool UserInputFlag { get; private set; }
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public bool TransparencyFlag { get; private set; }
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public ushort DelayTime { get; private set; }
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public byte TransparentColorIndex { get; private set; }
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private GraphicControlExtension() { }
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public static GraphicControlExtension Create(byte[] data, ref int offset) {
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Debug.Assert(data[offset] == EXTENSION_INTRODUCER &&
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data[offset + 1] == GRAPHIC_CONTROL_LABEL);
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GraphicControlExtension gce = new GraphicControlExtension();
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offset += 2;
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if (data[offset++] != 4) {
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Debug.WriteLine("Bad block size in GCE data");
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return null;
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}
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byte pak = data[offset++];
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gce.DisposalMethod = (byte)((pak >> 2) & 0x07);
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gce.UserInputFlag = (pak & 0x02) != 0;
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gce.TransparencyFlag = (pak & 0x01) != 0;
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gce.DelayTime = RawData.FetchLittleUshort(data, ref offset);
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gce.TransparentColorIndex = data[offset++];
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if (data[offset++] != 0) {
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Debug.WriteLine("Missing termination in GCE data");
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return null;
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}
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return gce;
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}
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}
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//
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// Image descriptor.
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//
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public const byte IMAGE_SEPARATOR = 0x2c;
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/// <summary>
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/// The graphic rendering block is an image descriptor, followed by an optional
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/// local color table, and then the image data itself.
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/// </summary>
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public class GraphicRenderingBlock {
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public ushort ImageLeftPosition { get; private set; }
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public ushort ImageTopPosition { get; private set; }
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public ushort ImageWidth { get; private set; }
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public ushort ImageHeight { get; private set; }
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public bool LocalColorTableFlag { get; private set; }
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public bool InterlaceFlag { get; private set; }
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public bool SortFlag { get; private set; }
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public byte LocalColorTableSize { get; private set; }
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//
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// Local color table.
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//
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public byte[] LocalColorTable { get; private set; }
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/// <summary>
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/// Offset of first byte of image data (which will be the LZW minimum code size byte).
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/// </summary>
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public int ImageStartOffset { get; private set; }
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public byte[] ImageData { get; private set; }
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/// <summary>
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/// Offset of last byte of image data (which will be the terminating $00 byte).
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/// </summary>
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public int ImageEndOffset { get; private set; }
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/// <summary>
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/// Optional extension with transparency and delay values.
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/// </summary>
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public GraphicControlExtension GraphicControlExt { get; set; }
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private GraphicRenderingBlock() { }
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public static GraphicRenderingBlock Create(byte[] data, ref int offset) {
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GraphicRenderingBlock grb = new GraphicRenderingBlock();
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//
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// Image descriptor.
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//
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Debug.Assert(data[offset] == IMAGE_SEPARATOR);
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offset++;
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grb.ImageLeftPosition = RawData.FetchLittleUshort(data, ref offset);
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grb.ImageTopPosition = RawData.FetchLittleUshort(data, ref offset);
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grb.ImageWidth = RawData.FetchLittleUshort(data, ref offset);
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grb.ImageHeight = RawData.FetchLittleUshort(data, ref offset);
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byte pak = data[offset++];
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grb.LocalColorTableFlag = (pak & 0x80) != 0;
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grb.InterlaceFlag = (pak & 0x40) != 0;
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grb.SortFlag = (pak & 0x20) != 0;
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grb.LocalColorTableSize = (byte)(pak & 0x07);
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//
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// Local color table (optional).
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//
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if (grb.LocalColorTableFlag) {
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// Size is expressed as a power of 2. TableSize=7 is 256 entries, 3 bytes each.
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int tableLen = 1 << (grb.LocalColorTableSize + 1);
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grb.LocalColorTable = new byte[tableLen * 3];
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for (int i = 0; i < tableLen * 3; i++) {
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grb.LocalColorTable[i] = data[offset++];
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}
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} else {
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grb.LocalColorTable = new byte[0];
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}
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//
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// Table based image data.
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//
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grb.ImageData = data;
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grb.ImageStartOffset = offset++;
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while (data[offset] != 0) {
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offset += data[offset] + 1;
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}
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grb.ImageEndOffset = offset++;
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return grb;
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}
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}
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public List<GraphicRenderingBlock> ImageBlocks = new List<GraphicRenderingBlock>();
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//
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// EOF marker.
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//
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public const byte GIF_TRAILER = 0x3b;
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/// <summary>
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/// Constructor. Internal only; use factory method.
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/// </summary>
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private UnpackedGif() { }
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/// <summary>
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/// </summary>
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/// <param name="gifData">GIF data stream. The array may be longer than the
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/// data stream.</param>
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/// <returns>Newly-created object, or null on error.</returns>
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public static UnpackedGif Create(byte[] gifData) {
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UnpackedGif gif = new UnpackedGif();
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try {
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if (!gif.Unpack(gifData)) {
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return null;
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}
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} catch (Exception ex) {
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Debug.WriteLine("Failure during GIF unpacking: " + ex);
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return null;
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}
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return gif;
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}
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private bool Unpack(byte[] gifData) {
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//
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// Header. Signature ("GIF") + version ("87a" or "89a").
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//
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if (RawData.CompareArrays(gifData, 0, GIF87A, 0, GIF87A.Length)) {
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FileVer = FileVersion.Gif87a;
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} else if (RawData.CompareArrays(gifData, 0, GIF89A, 0, GIF87A.Length)) {
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FileVer = FileVersion.Gif89a;
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} else {
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Debug.WriteLine("GIF signature not found");
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return false;
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}
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//Debug.WriteLine("GIF: found signature " + FileVer);
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byte pak;
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//
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// Logical screen descriptor.
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//
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int offset = GIF87A.Length;
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LogicalScreenWidth = RawData.FetchLittleUshort(gifData, ref offset);
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LogicalScreenHeight = RawData.FetchLittleUshort(gifData, ref offset);
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pak = gifData[offset++];
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GlobalColorTableFlag = (pak & 0x80) != 0;
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ColorResolution = (byte)((pak >> 4) & 0x07);
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SortFlag = (pak & 0x08) != 0;
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GlobalColorTableSize = (byte)(pak & 0x07);
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BackgroundColorIndex = gifData[offset++];
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PixelAspectRatio = gifData[offset++];
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//
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// Global color table.
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//
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if (GlobalColorTableFlag) {
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// Size is expressed as a power of 2. TableSize=7 is 256 entries, 3 bytes each.
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int tableLen = 1 << (GlobalColorTableSize + 1);
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GlobalColorTable = new byte[tableLen * 3];
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for (int i = 0; i < tableLen * 3; i++) {
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GlobalColorTable[i] = gifData[offset++];
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}
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} else {
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GlobalColorTable = new byte[0];
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}
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//
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// Various blocks follow. Continue until EOF is reached.
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//
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GraphicControlExtension lastGce = null;
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while (true) {
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if (offset >= gifData.Length) {
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Debug.WriteLine("Error: GIF unpacker ran off end of buffer");
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return false;
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}
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if (gifData[offset] == GIF_TRAILER) {
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break;
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} else if (gifData[offset] == EXTENSION_INTRODUCER) {
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if (gifData[offset + 1] == GRAPHIC_CONTROL_LABEL) {
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lastGce = GraphicControlExtension.Create(gifData, ref offset);
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} else {
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Debug.WriteLine("Skipping unknown extension 0x" +
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gifData[offset + 1].ToString("x2"));
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offset += 2;
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while (gifData[offset] != 0) {
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offset += gifData[offset] + 1;
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}
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offset++;
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}
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} else if (gifData[offset] == IMAGE_SEPARATOR) {
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GraphicRenderingBlock grb = GraphicRenderingBlock.Create(gifData, ref offset);
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if (grb != null) {
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if (lastGce != null) {
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grb.GraphicControlExt = lastGce;
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}
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ImageBlocks.Add(grb);
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}
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// this resets after the image
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lastGce = null;
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} else {
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Debug.WriteLine("Found unknown block start 0x" +
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gifData[offset].ToString("x2"));
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return false;
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}
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}
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return true;
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}
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public void DebugDump() {
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Debug.WriteLine("UnpackedGif: " + FileVer);
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Debug.WriteLine(" Logical size: " + LogicalScreenWidth + "x" + LogicalScreenHeight);
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Debug.WriteLine(" Global CT: " + GlobalColorTableFlag +
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" size=" + GlobalColorTableSize + " bkci=" + BackgroundColorIndex +
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" sort=" + SortFlag);
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Debug.WriteLine(" Aspect=" + PixelAspectRatio);
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Debug.WriteLine(" Images (" + ImageBlocks.Count + "):");
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foreach (GraphicRenderingBlock grb in ImageBlocks) {
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if (grb.GraphicControlExt != null) {
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GraphicControlExtension gce = grb.GraphicControlExt;
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Debug.WriteLine(" GCE: trans=" + gce.TransparencyFlag +
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" color=" + gce.TransparentColorIndex + " delay=" + gce.DelayTime +
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" disp=" + gce.DisposalMethod);
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} else {
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Debug.WriteLine(" No GCE");
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}
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Debug.WriteLine(" left=" + grb.ImageLeftPosition +
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" top=" + grb.ImageTopPosition + " width=" + grb.ImageWidth +
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" height=" + grb.ImageHeight);
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Debug.WriteLine(" localCT=" + grb.LocalColorTableFlag + " size=" +
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grb.LocalColorTableSize + " itrl=" + grb.InterlaceFlag);
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for (int i = 0; i < grb.LocalColorTable.Length; i += 3) {
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Debug.WriteLine(" " + (i / 3) + ": $" +
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grb.LocalColorTable[i].ToString("x2") + " $" +
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grb.LocalColorTable[i + 1].ToString("x2") + " $" +
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grb.LocalColorTable[i + 2].ToString("x2"));
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}
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}
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}
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}
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}
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