I'm not sure where to start with this so some guidance would be good. What I need to achieve is, examine a large image (say 1280x1024) and check to see if another smaller image exists within it or not (maybe a 50x50 pixel image).
I tried doing this by comparing every pixel which is really slow and I may need to do it 100+ times so it doesn't seem suitable. I'm just wondering if there is a better way?
Thanks
I was just working on something similar and the quick and dirty result I came up with is to use AForge.Net's implementation of "ExhaustiveTemplateMatching" with images 1/4 of their size. 720p images at full size took a couple minutes but at 1/4 size it's about a second on my puny computer.
public static class BitmapExtensions
{
/// <summary>
/// See if bmp is contained in template with a small margin of error.
/// </summary>
/// <param name="template">The Bitmap that might contain.</param>
/// <param name="bmp">The Bitmap that might be contained in.</param>
/// <returns>You guess!</returns>
public static bool Contains(this Bitmap template, Bitmap bmp)
{
const Int32 divisor = 4;
const Int32 epsilon = 10;
ExhaustiveTemplateMatching etm = new ExhaustiveTemplateMatching(0.9f);
TemplateMatch[] tm = etm.ProcessImage(
new ResizeNearestNeighbor(template.Width / divisor, template.Height / divisor).Apply(template),
new ResizeNearestNeighbor(bmp.Width / divisor, bmp.Height / divisor).Apply(bmp)
);
if (tm.Length == 1)
{
Rectangle tempRect = tm[0].Rectangle;
if (Math.Abs(bmp.Width / divisor - tempRect.Width) < epsilon
&&
Math.Abs(bmp.Height / divisor - tempRect.Height) < epsilon)
{
return true;
}
}
return false;
}
}
You could also of course just check for tm.length > 0 and yes there are some unnecessary divides in there :P
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