Resize Image to fit in bounding box

Question

An easy problem, but for some reason I just can't figure this out today.

I need to resize an image to the maximum possible size that will fit in a bounding box while maintaining the aspect ratio.

Basicly I'm looking for the code to fill in this function:

void CalcNewDimensions(ref int w, ref int h, int MaxWidth, int MaxHeight); 

Where w & h are the original height and width (in) and the new height and width (out) and MaxWidth and MaxHeight define the bounding box that the image must fit in.

Answer 1

Find which is smaller: MaxWidth / w or MaxHeight / h Then multiply w and h by that number

Explanation:

You need to find the scaling factor which makes the image fit.

To find the scaling factor, s, for the width, then s must be such that: s * w = MaxWidth. Therefore, the scaling factor is MaxWidth / w.

Similarly for height.

The one that requires the most scaling (smaller s) is the factor by which you must scale the whole image.

Answer 2

Based on Eric's suggestion I'd do something like this:

private static Size ExpandToBound(Size image, Size boundingBox) {            double widthScale = 0, heightScale = 0;     if (image.Width != 0)         widthScale = (double)boundingBox.Width / (double)image.Width;     if (image.Height != 0)         heightScale = (double)boundingBox.Height / (double)image.Height;                      double scale = Math.Min(widthScale, heightScale);      Size result = new Size((int)(image.Width * scale),                          (int)(image.Height * scale));     return result; } 

I might have gone a bit overboard on the casts, but I was just trying to preserve precision in the calculations.