Is there any way to measure similarity between two images?

[yut951121]

I want to compare various image compression methods and see what's most efficient but to do that I need to measure how much information is lost during compression. Is there any way or plugin to do this? Thanks in advance for your help.

[TechnoRobbo]

Load the compressed image as new layer above the original  (Layers Menu -> Import from File) and change it's blending mode to XOR (Layers Menu -> Layer Properties -> Blend Mode)

 

If the two images are identical then you will see a black canvas. If they are not then any differences will appear as strange colors on a black background.

[yut951121]

Load the compressed image as new layer above the original  (Layers Menu -> Import from File) and change it's blending mode to XOR (Layers Menu -> Layer Properties -> Blend Mode)

 

If the two images are identical then you will see a black canvas. If they are not then any differences will appear as strange colors on a black background.

I knew the xor trick, but is there any way to calculate a number out of it? (Like SSIM)

Edited October 25, 2014 by yut951121

[Ego Eram Reputo]

You could select the black (i.e. common pixels) then invert the selection to reach a count of dissimilar pixels.

[TechnoRobbo]

you can merge the layers  use this code lab code - it will give you difference percentage

0 would be identical , 100 would be completely different

 

Menu : Colors -> Difference

 

#region UICode

bool Amount1 = false; // [0,1] Slider 1 Description

#endregion

 

 

 

void Render(Surface dst, Surface src, Rectangle rect)

{

    if (!Amount1)

    {

        Amount1=true;

        int totalcount = src.Width * src.Height * 1020;

        int PixelSum = 0;

        ColorBgra CP;

        for (int y = 0; y < src.Height; y++)

        {

            for (int x =0; x < src.Width; x++)

            {

                CP = src[x,y];

                PixelSum  += CP.A;

                PixelSum  += CP.R;

                PixelSum  += CP.G;

                PixelSum  += CP.B;

 

            }

        }

        double result = (double)PixelSum / (double)totalcount;

        System.Windows.Forms.MessageBox.Show((100 * result).ToString()); 

    }

}

 

Difference.zip

[TechnoRobbo]

Uploaded a fix - should have multiplied by 1020 not 765

[yut951121]

Thanks very much everyone who replied for your hard work! This made my life much happier...