How to compare two images of different size ?

Alok Pandey

Hi ,

I want to compare two different size images (eg. img1, img2) and get a resultant image that
highlights the differences in img2. Please help me.

Thanks..

6 Replies

Know the answer? Post it — somebody with the same question will find it here.

Maen Badwan7y ago
There are different ways to compare two images and show the differences.
For example, you can combine the pixels of the two images with the operation Xor, which will zero-out all pixels in the target image that are identical to their counterparts in the source image. Another way is to compare the images intensities.
You can apply these types of comparisons (and others) using the image processing functions from LEADTOOLS. For example, you can use the CombineCommand or the CombineFastCommand classes with the OperationXor flag. The following LEADTOOLS C# code shows how you can do this:
using (RasterCodecs _codecs = new RasterCodecs())
{
//load the 2 images
using (RasterImage image1 = _codecs.Load("Img1.png"))
{
using (RasterImage images2 = _codecs.Load("Img2.png"))
{
//Perform XOR combining to convert similar pixels to black in image2. All non-similar pixels become non-black
LeadRect combineRect1 = new LeadRect(0, 0, image1.Width, image1.Height);
CombineFastCommand combineCmd = new CombineFastCommand(images2, combineRect1, new LeadPoint(0, 0), CombineFastCommandFlags.OperationXor);
combineCmd.Run(image1);
//Create a region in image2 with all the black pixels. Those pixels were the similar ones.
images2.AddColorToRegion(RasterColor.Black, RasterRegionCombineMode.Set);
//Fill the region with green
FillCommand fillGreen = new FillCommand(RasterColor.FromKnownColor(RasterKnownColor.Green));
fillGreen.Run(images2);
//Perform copy combining to copy the green pixels to the first image
combineCmd.DestinationImage = image1;
combineCmd.Flags = CombineFastCommandFlags.SourceCopy;
combineCmd.Run(images2);
//Save the result
_codecs.Save(image1, "Res.png", RasterImageFormat.Png, 24);
}
}
}
For more information, see the following links:
https://www.leadtools.com/help/leadtools/v20/dh/l/imageprocessing-combinefastcommand.html
https://www.leadtools.com/help/leadtools/v20/dh/pe/combinecommand.html
Sonu Gupta7y ago
Hi,

Visit the following URL -

https://social.msdn.microsoft.com/Forums/vstudio/en-US/d2676fa0-fa20-4e00-886b-812b851d62c8/how-do-i-compare-and-check-if-2-images-are-the-same-visually?forum=csharpgeneral
Atir Tahir7y ago
You can achieve this using GroupDocs.Comparison for .NET API. Please see this blog https://www.c-sharpcorner.com/blogs/pixel-by-pixel-image-comparison-in-net
The comparison starts with the upper left corner and compares the entire image pixel by pixel. If the pixels are the same, it moves on to the next one and so on until it finds a different one. The changed pixels are given an ID. It is defined as dabbed, deleted or changed. They are highlighted in a specific color (blue, red or green according to the standard settings).
Sanjay Kumar12y ago
Hi

http://blogs.msdn.com/b/domgreen/archive/2009/09/06/comparing-two-images-in-c.aspx
Dhirendra Misra12y ago
you can try these ones as well

http://www.c-sharpcorner.com/uploadfile/prathore/image-comparison-using-C-Sharp/

http://www.dotnetspider.com/resources/19811-Image-Compare-C.aspx
Jaganathan Bantheswaran12y ago
Hi,

Here is the nice C# example which you can even improve.