剪下一张图片的中心

Question

假设我有一张400x300px的图片，并且我希望将它剪成200x200px，将其置于服务器端（C＃，.NET 4.0）中。

我该怎么办？使用某种画布并移动它？任何教程/代码示例/建议？

Answer 1

创建具有目标大小的新的位图对象。

围绕该位图创建图形对象。

在Graphcs对象上，使用合适的参数调用DrawImage（），并从第一张图片中切出适当的段。

代码将是这样的：

Bitmap dstBitmap=new Bitmap(200, 200); 
using (Graphics g=Graphics.FromImage(dstBitmap)) 
{ 
    srcBitmap.DrawImage(dstBitmap, /* cropping parameters here */); 
} 
// at the end you'll have your bitmap in dstBitmap, ... 

我并没有包括对方法字面参数，使用智能感知和手册，以数字出来。

Answer 2

尝试这样：

 Bitmap sourceImage = ...; 

     int targetWidth = 200; 
     int targetHeight = 200; 

     int x = sourceImage.Width/2 - targetWidth/2; 
     int y = sourceImage.Height/2 - targetHeight/2; 

     Rectangle cropArea = 
      new Rectangle(x, y, targetWidth, targetHeight); 

     Bitmap targetImage = 
      sourceImage.Clone(cropArea, sourceImage.PixelFormat); 

如果源图像比目标图像尺寸更小，这显然会失败，但你的想法。

Answer 3

此方法将保存图像的中心，如果需要裁剪：

bool SaveCroppedImage(Image image, int targetWidth, int targetHeight, string filePath) 
{ 
    ImageCodecInfo jpgInfo = ImageCodecInfo.GetImageEncoders().Where(codecInfo => codecInfo.MimeType == "image/jpeg").First(); 
    Image finalImage = image; 
    System.Drawing.Bitmap bitmap = null; 
    try 
    { 
     int left = 0; 
     int top = 0; 
     int srcWidth = targetWidth; 
     int srcHeight = targetHeight; 
     bitmap = new System.Drawing.Bitmap(targetWidth, targetHeight); 
     double croppedHeightToWidth = (double)targetHeight/targetWidth; 
     double croppedWidthToHeight = (double)targetWidth/targetHeight; 

     if (image.Width > image.Height) 
     { 
      srcWidth = (int)(Math.Round(image.Height * croppedWidthToHeight)); 
      if (srcWidth < image.Width) 
      { 
       srcHeight = image.Height; 
       left = (image.Width - srcWidth)/2; 
      } 
      else 
      { 
       srcHeight = (int)Math.Round(image.Height * ((double)image.Width/srcWidth)); 
       srcWidth = image.Width; 
       top = (image.Height - srcHeight)/2; 
      } 
     } 
     else 
     { 
      srcHeight = (int)(Math.Round(image.Width * croppedHeightToWidth)); 
      if (srcHeight < image.Height) 
      { 
       srcWidth = image.Width; 
       top = (image.Height - srcHeight)/2; 
      } 
      else 
      { 
       srcWidth = (int)Math.Round(image.Width * ((double)image.Height/srcHeight)); 
       srcHeight = image.Height; 
       left = (image.Width - srcWidth)/2; 
      } 
     } 
     using (Graphics g = Graphics.FromImage(bitmap)) 
     { 
      g.SmoothingMode = SmoothingMode.HighQuality; 
      g.PixelOffsetMode = PixelOffsetMode.HighQuality; 
      g.CompositingQuality = CompositingQuality.HighQuality; 
      g.InterpolationMode = InterpolationMode.HighQualityBicubic; 
      g.DrawImage(image, new Rectangle(0, 0, bitmap.Width, bitmap.Height), new Rectangle(left, top, srcWidth, srcHeight), GraphicsUnit.Pixel); 
     } 
     finalImage = bitmap; 
    } 
    catch { } 
    try 
    { 
     using (EncoderParameters encParams = new EncoderParameters(1)) 
     { 
      encParams.Param[0] = new EncoderParameter(Encoder.Quality, (long)100); 
      //quality should be in the range [0..100] .. 100 for max, 0 for min (0 best compression) 
      finalImage.Save(filePath, jpgInfo, encParams); 
      return true; 
     } 
    } 
    catch { } 
    if (bitmap != null) 
    { 
     bitmap.Dispose(); 
    } 
    return false; 
}