c# - How to effectively crop and scale image data -

i need operate on pixel values in images. therefore wrote such class:

public class image_class {     #region property     public int width { get; private set; }     public int height { get; private set; }      byte[] buffer;     #endregion      #region constructors     public image_class()     {         ;     }     public image_class(int width, int height, byte[] data)     {         if (data.count() == (width * height * 3))         {             this.width = width;             this.height = height;              this.buffer = data;         }         else             throw new exception();     }     #endregion      #region bitmap     public imagesource bmp     {                 {             try             {                 var pixelformat = pixelformats.rgb24;                 var bytesperpixel = (pixelformat.bitsperpixel + 7) / 8;                 var stride = bytesperpixel * width;                  var bitmap = bitmapsource.create(width, height, 96d, 96d, pixelformat, null, buffer, stride);                  return bitmap;             }              catch { return null; }         }     }     #endregion      #region methods     public void load_from_file(string path)     {             var bmp = new bitmapimage();             bmp.begininit();             bmp.urisource = new uri(ofd.filename, urikind.absolute);             bmp.endinit();              height = (int)bmp.height;             width = (int)bmp.width;              int stride = width * ((bmp.format.bitsperpixel + 7) / 8);              int size = height * stride;              var buffer2 = new byte[size];             bmp.copypixels(buffer2, stride, 0);              buffer = new byte[size * 3 / 4];             (int = 0, j = 0; < size; += 4, j += 3)             {                 buffer[j] = buffer2[i + 2];                 buffer[j + 1] = buffer2[i + 1];                 buffer[j + 2] = buffer2[i];             }      }      public void load_from_file(string path, int width, int height)     {         this.width = width;         this.height = height;          var bmp = new bitmapimage();          bmp.begininit();         bmp.decodepixelheight = height;         bmp.decodepixelwidth = width;         bmp.urisource = new uri(path, urikind.absolute);         bmp.endinit();          int stride = width * ((bmp.format.bitsperpixel + 7) / 8);          int size = height * stride;          var buffer2 = new byte[size];         bmp.copypixels(buffer2, stride, 0);          buffer = new byte[size * 3 / 4];         (int = 0, j = 0; < size; += 4, j += 3)         {             buffer[j] = buffer2[i + 2];             buffer[j + 1] = buffer2[i + 1];             buffer[j + 2] = buffer2[i];         }      }       public void save_to_file(string path)     {         var pixelformat = pixelformats.rgb24;         var bytesperpixel = (pixelformat.bitsperpixel + 7) / 8;         var stride = bytesperpixel * width;          var encoder = new jpegbitmapencoder();          encoder.frames.add(bitmapframe.create(bitmapsource.create(width, height, 96d, 96d, pixelformat, null, buffer, stride)));          filestream fs = new filestream(path, filemode.openorcreate, fileaccess.readwrite);            encoder.save(fs);          fs.close();     }      public image_class cut(int x0, int y0, int dx, int dy)     {         if (x0 >= 0 & y0 >= 0 & x0 + dx <= width & y0 + dy <= height)         {             byte[] buffer3 = new byte[dx * dy * 3];              (int y = 0, = 0, j = -1; y < height; y++) (int x = 0; x < width; x++, += 3)                     if (x >= x0 & x < x0 + dx & y >= y0 & y < y0 + dy)                     {                         buffer3[++j] = buffer[i];                         buffer3[++j] = buffer[i + 1];                         buffer3[++j] = buffer[i + 2];                     }              return new image_class(dx, dy, buffer3);          }         else             throw new exception();     }     #endregion } 

the buffer array 1 use.

this class works fine. when need operate on data fragment of image, use method cut, example:

image_class img1=new image_class(); image_class img2=img1.cut(5,5,20,20); 

what need scale cut image other values , maintain format of pixel data. example want 50x50 square picture, scaled 20x20. do:

image_class img1=new image_class(); image_class img2=img1.cut(5,5,50,50); img2.save_to_file(path); image_class img3=new image_class(); img3.load_from_file(path, 20,20); 

it works, of course uneffective. can show me better solution?

you don't need this. in order copy rectangular part source bitmap, , subsequently scale it, might use croppedbitmap , transformedbitmap:

bitmapsource original = ... var crop = new croppedbitmap(original, new int32rect(5, 5, 50, 50)); var result = new transformedbitmap(crop, new scaletransform(0.4, 0.4));