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238 lines
No EOL
6.7 KiB
C#
238 lines
No EOL
6.7 KiB
C#
#region License Information (GPL v3)
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/*
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ShareX - A program that allows you to take screenshots and share any file type
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Copyright (c) 2007-2016 ShareX Team
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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Optionally you can also view the license at <http://www.gnu.org/licenses/>.
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*/
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#endregion License Information (GPL v3)
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using System;
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using System.Collections.Generic;
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using System.Drawing;
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using System.IO;
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namespace ShareX.HelpersLib
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{
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public class GifClass
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{
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public enum GIFVersion
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{
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GIF87a,
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GIF89a
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}
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public enum GIFBlockType
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{
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ImageDescriptor = 0x2C,
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Extension = 0x21,
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Trailer = 0x3B
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}
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public GIFVersion Version = GIFVersion.GIF87a;
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public List<byte> GifSignature = new List<byte>();
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public List<byte> ScreenDescriptor = new List<byte>();
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public List<byte> ColorTable = new List<byte>();
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public List<byte> ImageDescriptor = new List<byte>();
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public List<byte> ImageData = new List<byte>();
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public void LoadGifPicture(Image img, GIFQuality quality)
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{
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List<byte> dataList;
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using (MemoryStream ms = new MemoryStream())
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{
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img.SaveGIF(ms, quality);
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dataList = new List<byte>(ms.ToArray());
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}
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if (!AnalyzeGifSignature(dataList))
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{
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throw new Exception("File is not a gif!");
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}
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AnalyzeScreenDescriptor(dataList);
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GIFBlockType blockType = GetTypeOfNextBlock(dataList);
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while (blockType != GIFBlockType.Trailer)
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{
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switch (blockType)
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{
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case GIFBlockType.ImageDescriptor:
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AnalyzeImageDescriptor(dataList);
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break;
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case GIFBlockType.Extension:
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ThrowAwayExtensionBlock(dataList);
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break;
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}
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blockType = GetTypeOfNextBlock(dataList);
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}
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}
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private bool AnalyzeGifSignature(List<byte> gifData)
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{
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for (int i = 0; i < 6; i++)
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{
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GifSignature.Add(gifData[i]);
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}
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gifData.RemoveRange(0, 6);
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List<char> chars = GifSignature.ConvertAll(ByteToChar);
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string s = new string(chars.ToArray());
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if (s == GIFVersion.GIF89a.ToString())
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{
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Version = GIFVersion.GIF89a;
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}
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else if (s == GIFVersion.GIF87a.ToString())
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{
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Version = GIFVersion.GIF87a;
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}
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else
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{
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return false;
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}
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return true;
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}
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private char ByteToChar(byte b)
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{
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return (char)b;
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}
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private void AnalyzeScreenDescriptor(List<byte> gifData)
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{
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for (int i = 0; i < 7; i++)
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{
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ScreenDescriptor.Add(gifData[i]);
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}
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gifData.RemoveRange(0, 7);
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// if the first bit of the fifth byte is set the GlobelColorTable follows this block
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bool globalColorTableFollows = (ScreenDescriptor[4] & 0x80) != 0;
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if (globalColorTableFollows)
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{
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int pixel = ScreenDescriptor[4] & 0x07;
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int lengthOfColorTableInByte = 3 * ((int)Math.Pow(2, pixel + 1));
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for (int i = 0; i < lengthOfColorTableInByte; i++)
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{
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ColorTable.Add(gifData[i]);
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}
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gifData.RemoveRange(0, lengthOfColorTableInByte);
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}
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ScreenDescriptor[4] = (byte)(ScreenDescriptor[4] & 0x7F);
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}
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private GIFBlockType GetTypeOfNextBlock(List<byte> gifData)
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{
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GIFBlockType blockType = (GIFBlockType)gifData[0];
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return blockType;
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}
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private void AnalyzeImageDescriptor(List<byte> gifData)
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{
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for (int i = 0; i < 10; i++)
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{
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ImageDescriptor.Add(gifData[i]);
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}
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gifData.RemoveRange(0, 10);
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// get ColorTable if exists
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bool localColorMapFollows = (ImageDescriptor[9] & 0x80) != 0;
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if (localColorMapFollows)
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{
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int pixel = ImageDescriptor[9] & 0x07;
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int lengthOfColorTableInByte = 3 * ((int)Math.Pow(2, pixel + 1));
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ColorTable.Clear();
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for (int i = 0; i < lengthOfColorTableInByte; i++)
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{
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ColorTable.Add(gifData[i]);
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}
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gifData.RemoveRange(0, lengthOfColorTableInByte);
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}
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else
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{
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int lastThreeBitsOfGlobalTableDescription = ScreenDescriptor[4] & 0x07;
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ImageDescriptor[9] = (byte)(ImageDescriptor[9] & 0xF8);
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ImageDescriptor[9] = (byte)(ImageDescriptor[9] | lastThreeBitsOfGlobalTableDescription);
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}
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ImageDescriptor[9] = (byte)(ImageDescriptor[9] | 0x80);
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GetImageData(gifData);
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}
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private void GetImageData(List<byte> gifData)
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{
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ImageData.Add(gifData[0]);
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gifData.RemoveAt(0);
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while (gifData[0] != 0x00)
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{
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int countOfFollowingDataBytes = gifData[0];
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for (int i = 0; i <= countOfFollowingDataBytes; i++)
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{
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ImageData.Add(gifData[i]);
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}
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gifData.RemoveRange(0, countOfFollowingDataBytes + 1);
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}
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ImageData.Add(gifData[0]);
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gifData.RemoveAt(0);
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}
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private void ThrowAwayExtensionBlock(List<byte> gifData)
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{
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gifData.RemoveRange(0, 2); // Delete ExtensionBlockIndicator and ExtensionDetermination
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while (gifData[0] != 0)
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{
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gifData.RemoveRange(0, gifData[0] + 1);
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}
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gifData.RemoveAt(0);
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}
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}
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} |