需要在nuget安装包System.Drawing.Common
using System;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Drawing.Imaging;
using System.IO;
/// <summary>
/// 生成缩略图，针对GIF图片
/// </summary>
/// <param name="imgPath">输入文件地址</param>
/// <param name="savePath">保存文件地址</param>
/// <param name="width">压缩输出宽度</param>
/// <param name="height">压缩输出高度</param>
public static void GifYasuo(string imgPath, string savePath, int width, int height)
{
//原图
Image img = Image.FromFile(imgPath);
//不够100*100的不缩放
if (img.Width > 100 && img.Height > 100)
{
//按比例缩放
if (img.Width > width)
{
height = width * img.Height / img.Width;
}
//新图第一帧
Image new_img = new Bitmap(width, height);
//新图其他帧
Image new_imgs = new Bitmap(width, height);
//新图第一帧GDI+绘图对象
Graphics g_new_img = Graphics.FromImage(new_img);
//新图其他帧GDI+绘图对象
Graphics g_new_imgs = Graphics.FromImage(new_imgs);
//配置新图第一帧GDI+绘图对象
g_new_img.CompositingMode = CompositingMode.SourceCopy;
g_new_img.InterpolationMode = InterpolationMode.HighQualityBicubic;
g_new_img.PixelOffsetMode = PixelOffsetMode.HighQuality;
g_new_img.SmoothingMode = SmoothingMode.HighQuality;
g_new_img.Clear(Color.FromKnownColor(KnownColor.Transparent));
//配置其他帧GDI+绘图对象
g_new_imgs.CompositingMode = CompositingMode.SourceCopy;
g_new_imgs.InterpolationMode = InterpolationMode.HighQualityBicubic;
g_new_imgs.PixelOffsetMode = PixelOffsetMode.HighQuality;
g_new_imgs.SmoothingMode = SmoothingMode.HighQuality;
g_new_imgs.Clear(Color.FromKnownColor(KnownColor.Transparent));
质量设置
//EncoderParameters qualityEncoder = new EncoderParameters(1);
//long[] qy = new long[1];
//qy[0] = flag;//设置压缩的比例1-100
//var ep_quality = new EncoderParameter(Encoder.Quality, qy);
//qualityEncoder.Param[0] = ep_quality;
//遍历维数
foreach (Guid gid in img.FrameDimensionsList)
{
//因为是缩小GIF文件所以这里要设置为Time
//如果是TIFF这里要设置为PAGE
FrameDimension f = FrameDimension.Time;
//获取总帧数
int count = img.GetFrameCount(f);
//保存标示参数
Encoder encoder = Encoder.SaveFlag;
//
EncoderParameters ep = null;
//图片编码、解码器
ImageCodecInfo ici = null;
//图片编码、解码器集合
ImageCodecInfo[] icis = ImageCodecInfo.GetImageDecoders();
//为 图片编码、解码器 对象 赋值
foreach (ImageCodecInfo ic in icis)
{
if (ic.FormatID == ImageFormat.Gif.Guid)
{
ici = ic;
break;
}
}
//每一帧
for (int c = 0; c < count; c++)
{
//选择由维度和索引指定的帧
img.SelectActiveFrame(f, c);
//第一帧
if (c == 0)
{
//将原图第一帧画给新图第一帧
g_new_img.DrawImage(img, new Rectangle(0, 0, width, height), new Rectangle(0, 0, img.Width, img.Height), GraphicsUnit.Pixel);
//把振频和透明背景调色板等设置复制给新图第一帧
for (int i = 0; i < img.PropertyItems.Length; i++)
{
new_img.SetPropertyItem(img.PropertyItems[i]);
}
ep = new EncoderParameters(1);
//第一帧需要设置为MultiFrame
ep.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.MultiFrame);
//ep.Param[1] = eParam;
//保存第一帧
new_img.Save(savePath, ici, ep);
}
//其他帧
else
{
//把原图的其他帧画给新图的其他帧
g_new_imgs.DrawImage(img, new Rectangle(0, 0, width, height), new Rectangle(0, 0, img.Width, img.Height), GraphicsUnit.Pixel);
//把振频和透明背景调色板等设置复制给新图第一帧
for (int i = 0; i < img.PropertyItems.Length; i++)
{
new_imgs.SetPropertyItem(img.PropertyItems[i]);
}
ep = new EncoderParameters(1);
//如果是GIF这里设置为FrameDimensionTime
//如果为TIFF则设置为FrameDimensionPage
ep.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.FrameDimensionTime);
//向新图添加一帧
new_img.SaveAdd(new_imgs, ep);
//whl添加，设置保存质量
//new_img.SaveAdd(qualityEncoder);
}
}
ep = new EncoderParameters(1);
//关闭多帧文件流
ep.Param[0] = new EncoderParameter(encoder, (long)EncoderValue.Flush);
new_img.SaveAdd(ep);
}
//whl添加，设置保存质量
//图片编码、解码器
ImageCodecInfo ici2 = null;
//图片编码、解码器集合
ImageCodecInfo[] icis2 = ImageCodecInfo.GetImageDecoders();
//为 图片编码、解码器 对象 赋值
foreach (ImageCodecInfo ic in icis2)
{
if (ic.FormatID == ImageFormat.Gif.Guid)
{
ici2 = ic;
break;
}
}
//释放文件
img.Dispose();
new_img.Dispose();
new_imgs.Dispose();
g_new_img.Dispose();
g_new_imgs.Dispose();
}
}