最近,项目上涉及到了图像压缩,发现原有的图像压缩功能,虽然保证了图像的大小300K以内,但是压缩后的图像看的不在清晰,并且,限定了图片的Height或者是Width。
看到了一个压缩算法:C#无损高质量压缩图片代码
进过测试这个算法,发现,将原始图像的大小进行对半处理,然后迭代跳转压缩质量参数,可以得到不错的效果。
修改后的算法如下:
/// <summary>
/// 无损压缩图片
/// </summary>
/// <param name="sFile">原图片地址</param>
/// <param name="dFile">压缩后保存图片地址</param>
/// <param name="flag">压缩质量(数字越小压缩率越高)1-100</param>
/// <param name="size">压缩后图片的最大大小</param>
/// <param name="sfsc">是否是第一次调用</param>
/// <returns></returns>
public static bool CompressImage(string sFile, string dFile, int flag = 90, int size = 300, bool sfsc = true)
{
Image iSource = Image.FromFile(sFile);
ImageFormat tFormat = iSource.RawFormat;
//如果是第一次调用,原始图像的大小小于要压缩的大小,则直接复制文件,并且返回true
FileInfo firstFileInfo = new FileInfo(sFile);
if (sfsc == true && firstFileInfo.Length < size * 1024)
{
firstFileInfo.CopyTo(dFile);
return true;
}
int dHeight = iSource.Height / 2;
int dWidth = iSource.Width / 2;
int sW = 0, sH = 0;
//按比例缩放
Size tem_size = new Size(iSource.Width, iSource.Height);
if (tem_size.Width > dHeight || tem_size.Width > dWidth)
{
if ((tem_size.Width * dHeight) > (tem_size.Width * dWidth))
{
sW = dWidth;
sH = (dWidth * tem_size.Height) / tem_size.Width;
}
else
{
sH = dHeight;
sW = (tem_size.Width * dHeight) / tem_size.Height;
}
}
else
{
sW = tem_size.Width;
sH = tem_size.Height;
}
Bitmap ob = new Bitmap(dWidth, dHeight);
Graphics g = Graphics.FromImage(ob);
g.Clear(Color.WhiteSmoke);
g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel);
g.Dispose();
//以下代码为保存图片时,设置压缩质量
EncoderParameters ep = new EncoderParameters();
long[] qy = new long[1];
qy[0] = flag;//设置压缩的比例1-100
EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy);
ep.Param[0] = eParam;
try
{
ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
ImageCodecInfo jpegICIinfo = null;
for (int x = 0; x < arrayICI.Length; x++)
{
if (arrayICI[x].FormatDescription.Equals("JPEG"))
{
jpegICIinfo = arrayICI[x];
break;
}
}
if (jpegICIinfo != null)
{
ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径
FileInfo fi = new FileInfo(dFile);
if (fi.Length > 1024 * size)
{
flag = flag - 10;
CompressImage(sFile, dFile, flag, size, false);
}
}
else
{
ob.Save(dFile, tFormat);
}
return true;
}
catch
{
return false;
}
finally
{
iSource.Dispose();
ob.Dispose();
}
}
效果图如下:
第一张的大小是2.82M,尺寸是3680*4640。
第二张的大小是274KB,尺寸是1740*2320,清晰度方面还是不错的。
以上就是本文的全部内容,希望对大家的学习有所帮助
/// <summary>
/// 图像缩略图处理
/// </summary>
/// <param name="bytes">图像源数据</param>
/// <param name="compression">压缩质量 1-100</param>
/// <param name="thumbWidth">缩略图的宽</param>
/// <param name="thumbHeight">缩略图的高</param>
/// <returns></returns>
public static byte[] ConvertToThumbnail(byte[] bytes, int compression = 100, int thumbWidth = 0, int thumbHeight = 0)
{
byte[] bs = null;
try
{
if (bytes != null)
{
using (MemoryStream ms = new MemoryStream(bytes))
{
using (Bitmap srcimg = new Bitmap(ms))
{
if (thumbWidth == 0 && thumbHeight == 0)
{
thumbWidth = srcimg.Width;
thumbHeight = srcimg.Height;
}
using (Bitmap dstimg = new Bitmap(thumbWidth, thumbHeight))//图片压缩质量
{
//从Bitmap创建一个System.Drawing.Graphics对象,用来绘制高质量的缩小图。
using (Graphics gr = Graphics.FromImage(dstimg))
{
//把原始图像绘制成上面所设置宽高的缩小图
Rectangle rectDestination = new Rectangle(0, 0, thumbWidth, thumbHeight);
gr.Clear(Color.WhiteSmoke);
gr.CompositingQuality = CompositingQuality.HighQuality;
gr.SmoothingMode = SmoothingMode.HighQuality;
gr.InterpolationMode = InterpolationMode.HighQualityBicubic;
gr.DrawImage(srcimg, rectDestination, 0, 0, srcimg.Width, srcimg.Height, GraphicsUnit.Pixel);
EncoderParameters ep = new EncoderParameters(1);
ep.Param[0] = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, compression);//设置压缩的比例1-100
ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders();
ImageCodecInfo jpegICIinfo = arrayICI.FirstOrDefault(t => t.FormatID == System.Drawing.Imaging.ImageFormat.Png.Guid);
using (MemoryStream dstms = new MemoryStream())
{
if (jpegICIinfo != null)
{
dstimg.Save(dstms, jpegICIinfo, ep);
}
else
{
dstimg.Save(dstms, System.Drawing.Imaging.ImageFormat.Png);//保存到内存里
}
bs = new Byte[dstms.Length];
dstms.Position = 0;
dstms.Read(bs, 0, bs.Length);
}
}
}
}
}
}
}
catch (Exception ex)
{
LogManager.DefaultLogger.Error(LogConvert.ParseWebEx(ex), string.Concat("ConvertToThumbnail error.", thumbWidth, " ", thumbHeight));
}
return bs;
}
有时候需要一些图片,但是太大了,又有限制,所以想到如何把一张图片的内存大小给缩小,这样就OK了。
1.代码如下:
借鉴:https://docs.microsoft.com/zh-cn/dotnet/api/system.drawing.imaging.encoderparameter?view=netframework-4.6
using System;
using System.Drawing;
using System.Drawing.Imaging;
//这里面有示例文档代码
//https://docs.microsoft.com/zh-cn/dotnet/api/system.drawing.imaging.encoderparameter?view=netframework-4.6
namespace WindowsFormsApp1 {
class MyTool {
//根据原图,得到压缩图片并保存在桌面,返回压缩图路径
public static String compressImage(String bmpPath , int quality) {
//原图路径
Bitmap bmp = new Bitmap(bmpPath);
ImageCodecInfo codecInfo = GetEncoder(bmp.RawFormat); //图片编解码信息
System.Drawing.Imaging.Encoder encoder = System.Drawing.Imaging.Encoder.Quality;
EncoderParameters encoderParameters = new EncoderParameters(1);
EncoderParameter encoderParameter = new EncoderParameter(encoder , quality);
encoderParameters.Param[0] = encoderParameter; //编码器参数
//压缩图路径
ImageFormat format = bmp.RawFormat;
String newFilePath = String.Empty; //压缩图所在路径
// Guid.NewGuid().ToString()
//GUID 是一个 128 位整数 (16 个字节),它可用于跨所有计算机和网络中,任何唯一标识符是必需的。 此类标识符具有重复的可能性非常小
String deskPath = Environment.GetFolderPath(Environment.SpecialFolder.Desktop);
if (format.Equals(ImageFormat.Jpeg)) {
newFilePath = deskPath + @"\" + Guid.NewGuid().ToString() + ".jpeg";
}
else if (format.Equals(ImageFormat.Png)) {
newFilePath = deskPath + @"\" + Guid.NewGuid().ToString() + ".png";
}
else if (format.Equals(ImageFormat.Bmp)) {
newFilePath = deskPath + @"\" + Guid.NewGuid().ToString() + ".bmp";
}
else if (format.Equals(ImageFormat.Gif)) {
newFilePath = deskPath + @"\" + Guid.NewGuid().ToString() + ".gif";
}
else if (format.Equals(ImageFormat.Icon)) {
newFilePath = deskPath + @"\" + Guid.NewGuid().ToString() + ".icon";
}
else {
newFilePath = deskPath + @"\" + Guid.NewGuid().ToString() + ".jpg";
}
bmp.Save(newFilePath , codecInfo , encoderParameters); //保存压缩图
return newFilePath; //返回压缩图路径
}
private static ImageCodecInfo GetEncoder(ImageFormat rawFormat) {
ImageCodecInfo[] codecs = ImageCodecInfo.GetImageDecoders();
foreach (ImageCodecInfo codec in codecs) {
if (codec.FormatID == rawFormat.Guid) {
return codec;
}
}
return null;
}
}
}
然后调用:
private void button1_Click_1(object sender, EventArgs e) {
using (OpenFileDialog ofd = new OpenFileDialog()) {
ofd.Filter = "图片|*.jpg;*.png;*.gif;*.jpeg;*.bmp";
if (ofd.ShowDialog() == DialogResult.OK) {
String b = MyTool.compressImage(ofd.FileName , 50);
}
}
}
2.结果
我试了把一张大于2M的图片压缩成了400多KB。