Question

So I’m in need of some resizing.

I found two different methods.

One looks like this:

public static Byte[] ResizeImageNew(System.Drawing.Image imageFile, int targetWidth, int targetHeight) {
        using(imageFile){
            Size newSize = CalculateDimensions(imageFile.Size, targetWidth, targetHeight);

            using (Bitmap newImage = new Bitmap(newSize.Width, newSize.Height, PixelFormat.Format32bppRgb)) {
                newImage.SetResolution(imageFile.HorizontalResolution, imageFile.VerticalResolution);
                using (Graphics canvas = Graphics.FromImage(newImage)) {
                    canvas.SmoothingMode = SmoothingMode.AntiAlias;
                    canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
                    canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
                    canvas.DrawImage(imageFile, new Rectangle(new Point(0, 0), newSize));
                    MemoryStream m = new MemoryStream();
                    newImage.Save(m, ImageFormat.Jpeg);
                    return m.GetBuffer();
                }
            }
        }
    }

And the other:

    public static System.Drawing.Image ResizeImage(System.Drawing.Image originalImage, int width, int maxHeight) {
        originalImage.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipNone);
        originalImage.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipNone);

        int NewHeight = originalImage.Height * width / originalImage.Width;
        if (NewHeight > maxHeight) {
            // Resize with height instead
            width = originalImage.Width * maxHeight / originalImage.Height;
            NewHeight = maxHeight;
        }

        System.Drawing.Image newImage = originalImage.GetThumbnailImage(width, NewHeight, null, IntPtr.Zero);

        return newImage;
    }

I basically ‘borrowed’ both methods, and just changed bits and pieces.

However – using the first one, whenever I resize to a little smaller picture, the size of the file is actually larger then the original (!?)

And the second while greatly improving size looks terrible :/

I’m of course leaning on merely improving image quality in the first method, if possible, but I can’t see how, everything looks to be ‘high quality’ from my point of view ?

Answer 1

You may have to set the JPEG compression level. Currently it probably saves at a very high quality level, which may not be what you desire.

See here for more info: http://msdn.microsoft.com/en-us/library/bb882583.aspx

Note, however, that just reducing the resolution of the image doesn’t necessarily reduce filesize. Due to how compression works, a smaller resolution file that has been blurred due to interpolation modes can be significantly larger than the original, though with JPEG that’s probably not a big concern due to the lossy algorithm. It can make a huge difference for PNGs, though, if the original file was very simple before (like “flat” webcomic or simple vector graphics) and has been blurred after resizing.