Crop/Remove Unwanted Space at the edges of image

Question

I have search a lot to remove the unwanted space but could not found. I only found links which can used to remove black and white background space. But my background images

Answer 1

Here's a more reliable approach that uses a Sobel energy filter and a fast bounding box detection routine (extracted from the WhitespaceTrimmer plugin for ImageResizer).

namespace ImageResizer.Plugins.WhitespaceTrimmer {
public class BoundingBoxFinder {

    /// 

    /// Returns a rectangle inside 'lookInside' that bounds any energy greater than 'threshold'. 
    /// 
    /// 
    /// A rectangle of 'image' to look inside. 
    /// 1-255, the energy threshold to detect activity. 80-150 is a good range.
    /// 
    public Rectangle FindBoxSobel(Bitmap originalImage, Rectangle lookInside, byte threshold) {

        Bitmap image = originalImage;
        try {
            //Convert if needed (makes an extra copy)
            if (image.PixelFormat != PixelFormat.Format24bppRgb &&
                image.PixelFormat != PixelFormat.Format32bppArgb &&
                image.PixelFormat != PixelFormat.Format32bppRgb) {
                image = AForge.Imaging.Image.Clone(image, PixelFormat.Format24bppRgb);
            }

            //Crop if needed (makes an extra copy unless we converted too, then only 1 extra copy)
            if (!lookInside.Equals(new Rectangle(0, 0, image.Width, image.Height))) {
                Bitmap oldImage = image;
                try {
                    image = new Crop(lookInside).Apply(image);
                } finally {
                    if (oldImage != originalImage) oldImage.Dispose(); //Dispose the cloned 
                }
            }


            //Makes 1 more copy at 1/3rd the size, in grayscale
            Rectangle result = FindBoxSobel(image, threshold);
            return new Rectangle(lookInside.X + result.X, lookInside.Y + result.Y, result.Width, result.Height);


        } finally {
            if (image != originalImage) image.Dispose();
        }

    }
    /// 

    /// Requires 24 bit or 32 bit (A) RGB image. 
    /// 
    /// 
    /// 
    /// 
    public Rectangle FindBoxSobel(Bitmap rgb, byte threshold) {
        using (Bitmap gray = Grayscale.CommonAlgorithms.Y.Apply(rgb)) {

            //Apply sobel operator to grayscale image
            new SobelEdgeDetector().ApplyInPlace(gray);
            //Threshold into black and white.
            new Threshold(threshold).ApplyInPlace(gray);
            //Trim only exact black pixels
            // lock source bitmap data
            BitmapData data = gray.LockBits(new Rectangle(0, 0, gray.Width, gray.Height), ImageLockMode.ReadOnly, gray.PixelFormat);
            try {
                return FindBoxExactGrayscale(data, 0);
            } finally {
                gray.UnlockBits(data);
            }
        }
    }
    /// 

    /// Returns a bounding box that only excludes the specified color. 
    /// Only works on 8-bit images.
    /// 
    /// 
    /// The palette index to remove.
    /// 
    public Rectangle FindBoxExactGrayscale(BitmapData sourceData, byte indexToRemove) {
        if (sourceData.PixelFormat != PixelFormat.Format8bppIndexed) throw new ArgumentOutOfRangeException("FindBoxExact only operates on 8-bit grayscale images");
        // get source image size
        int width = sourceData.Width;
        int height = sourceData.Height;
        int offset = sourceData.Stride - width;

        int minX = width;
        int minY = height;
        int maxX = 0;
        int maxY = 0;

        // find rectangle which contains something except color to remove
        unsafe {
            byte* src = (byte*)sourceData.Scan0;

            for (int y = 0; y < height; y++) {
                if (y > 0) src += offset; //Don't adjust for offset until after first row
                for (int x = 0; x < width; x++) {
                    if (x > 0 || y > 0) src++; //Don't increment until after the first pixel.
                    if (*src != indexToRemove) {
                        if (x < minX)
                            minX = x;
                        if (x > maxX)
                            maxX = x;
                        if (y < minY)
                            minY = y;
                        if (y > maxY)
                            maxY = y;
                    }
                }
            }
        }

        // check
        if ((minX == width) && (minY == height) && (maxX == 0) && (maxY == 0)) {
            minX = minY = 0;
        }

        return new Rectangle(minX,minY,maxX - minX + 1, maxY - minY + 1);
    }
}
}