Question

I have a fixed-size canvas (e.g. presentation slide). Need to embed a picture into it without any quality distortion. If the image is smaller than the canvas, it must be centered. If it’s larger, it has to be scaled down to fit.

Does any reliable algorithm exist or I have to create it from scratch?

Answer 1

The scaling you need is simply

scale = desired size / actual size

To avoid distortion you apply the same scale to both the height and width.

To ensure you get the right size you find the longest dimension and scale using that so your code becomes:

if (height > width)
{
    scale = desiredHeight / actualHeight;
}
else
{
    scale = desiredWidth / actualWidth;
}

Make sure you’ve converted the height and width to double values to avoid integer arithmetic.