How to crop an image using C#?

Question

How can I write an application that will crop images in C#?

Answer 1

I was looking for a easy and FAST function with no additional libary to do the job. I tried Nicks solution, but i needed 29,4 sec to "extract" 1195 images of an atlas file. So later i managed this way and needed 2,43 sec to do the same job. Maybe this will be helpful.

// content of the Texture class
public class Texture
{
    //name of the texture
    public string name { get; set; }
    //x position of the texture in the atlas image
    public int x { get; set; }
    //y position of the texture in the atlas image
    public int y { get; set; }
    //width of the texture in the atlas image
    public int width { get; set; }
    //height of the texture in the atlas image
    public int height { get; set; }
}

Bitmap atlasImage = new Bitmap(@"C:\somepicture.png");
PixelFormat pixelFormat = atlasImage.PixelFormat;

foreach (Texture t in textureList)
{
     try
     {
           CroppedImage = new Bitmap(t.width, t.height, pixelFormat);
           // copy pixels over to avoid antialiasing or any other side effects of drawing
           // the subimages to the output image using Graphics
           for (int x = 0; x < t.width; x++)
               for (int y = 0; y < t.height; y++)
                   CroppedImage.SetPixel(x, y, atlasImage.GetPixel(t.x + x, t.y + y));
           CroppedImage.Save(Path.Combine(workingFolder, t.name + ".png"), ImageFormat.Png);
     }
     catch (Exception ex)
     {
          // handle the exception
     }
}

Answer 2

You can use Graphics.DrawImage to draw a cropped image onto the graphics object from a bitmap.

Rectangle cropRect = new Rectangle(...);
Bitmap src = Image.FromFile(fileName) as Bitmap;
Bitmap target = new Bitmap(cropRect.Width, cropRect.Height);

using(Graphics g = Graphics.FromImage(target))
{
   g.DrawImage(src, new Rectangle(0, 0, target.Width, target.Height), 
                    cropRect,                        
                    GraphicsUnit.Pixel);
}