scaling an image, but keep its proportions

Question

I want to scale images, but I don't want the image to look skewed.

The image has to be 115x115 (length x width).

The image can't be over 115 pixels high (length), but if needed, the width can be less than 115 but not more.

Is this tricky?

Answer 1

You're looking to scale an image and preserve Aspect Ratio:

float MaxRatio = MaxWidth / (float) MaxHeight;
float ImgRatio = source.Width / (float) source.Height;

if (source.Width > MaxWidth)
return new Bitmap(source, new Size(MaxWidth, (int) Math.Round(MaxWidth /
ImgRatio, 0)));

if (source.Height > MaxHeight)
return new Bitmap(source, new Size((int) Math.Round(MaxWidth * ImgRatio,
0), MaxHeight));

return source;

Should help you, and if you're interested in the idea:

Wikpedia article on Image Aspect Ratio http://bit.ly/d4klf

Answer 2

Take a look at Bertrands blog post about scaling images using GDI and WPF.

Answer 3

You need to preserve aspect ratio:

float scale = 0.0;

    if (newWidth > maxWidth || newHeight > maxHeight)
    {
        if (maxWidth/newWidth < maxHeight/newHeight)
        {
            scale = maxWidth/newWidth;
        }
        else
        {
            scale = maxHeight/newHeight;
        }
        newWidth = newWidth*scale;
        newHeight = newHeight*scale;

    }

In the code, Initially newWidth/newHeight are width/Height of image.