logicalscreendescriptor.cs

gif图像处理 包括对多帧gif动画的缩放

#region Copyright & License
/*----------------------------------------------------------------
// Copyright (C) 2008 jillzhang 版权所有。 
//  
// 文件名：LogicalScreenDescriptor.cs
// 文件功能描述：
// 
// 创建标识：jillzhang 
// 修改标识：
// 修改描述：
//
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//----------------------------------------------------------------*/

/*-------------------------New BSD License ------------------
 Copyright (c) 2008, jillzhang
All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

* Neither the name of jillzhang nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 */
#endregion

using System;
using System.Collections.Generic;
using System.Text;
using System.IO;

namespace Jillzhang.GifUtility
{
    #region 类LogicalScreenDescriptor
    /// <summary>
    /// 逻辑屏幕标识符(Logical Screen Descriptor)
    /// </summary>
    internal class LogicalScreenDescriptor
    {
        private short _width;
        /// <summary>
        /// 逻辑屏幕宽度 像素数，定义GIF图象的宽度
        /// </summary>
        internal short Width
        {
            get { return _width; }
            set { _width = value; }
        }

        private short _height;

        /// <summary>
        /// 逻辑屏幕高度 像素数，定义GIF图象的高度
        /// </summary>
        internal short Height
        {
            get { return _height; }
            set { _height = value; }
        }


        private byte _packed;

        internal byte Packed
        {
            get { return _packed; }
            set { _packed = value; }
        }

        private byte _bgIndex;
        /// <summary>
        /// 背景色,背景颜色(在全局颜色列表中的索引，如果没有全局颜色列表，该值没有意义)
        /// </summary>
        internal byte BgColorIndex
        {
            get { return _bgIndex; }
            set { _bgIndex = value; }
        }


        private byte _pixelAspect;
        /// <summary>
        /// 像素宽高比,像素宽高比(Pixel Aspect Radio)
        /// </summary>
        internal byte PixcelAspect
        {
            get { return _pixelAspect; }
            set { _pixelAspect = value; }
        }
        private bool _globalColorTableFlag;
        /// <summary>
        /// m - 全局颜色列表标志(Global Color Table Flag)，当置位时表示有全局颜色列表，pixel值有意义.
        /// </summary>
        internal bool GlobalColorTableFlag
        {
            get { return _globalColorTableFlag; }
            set { _globalColorTableFlag = value; }
        }

        private byte _colorResoluTion;
        /// <summary>
        /// cr - 颜色深度(Color ResoluTion)，cr+1确定图象的颜色深度.
        /// </summary>
        internal byte ColorResoluTion
        {
            get { return _colorResoluTion; }
            set { _colorResoluTion = value; }
        }

        private int _sortFlag;

        /// <summary>
        /// s - 分类标志(Sort Flag)，如果置位表示全局颜色列表分类排列.
        /// </summary>
        internal int SortFlag
        {
            get { return _sortFlag; }
            set { _sortFlag = value; }
        }

        private int _globalColorTableSize;
        /// <summary>
        /// 全局颜色列表大小，pixel+1确定颜色列表的索引数（2的pixel+1次方）.
        /// </summary>
        internal int GlobalColorTableSize
        {
            get { return _globalColorTableSize; }
            set { _globalColorTableSize = value; }
        }
           

        internal byte[] GetBuffer()
        {
            byte[] buffer = new byte[7];
            Array.Copy(BitConverter.GetBytes(_width), 0, buffer, 0, 2);
            Array.Copy(BitConverter.GetBytes(_height), 0, buffer, 2, 2);
            int m = 0;
            if (_globalColorTableFlag)
            {
                m = 1;
            }
            byte pixel = (byte)(Math.Log(_globalColorTableSize,2) - 1);
            _packed = (byte)(pixel | (_sortFlag << 4)|(_colorResoluTion<<5)|(m<<7));
            buffer[4] = _packed;
            buffer[5] = _bgIndex;
            buffer[6] = _pixelAspect;
            return buffer;
        }
    }
    #endregion
}