Help in subtraction of two images

Question

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Help!
The subtraction of two images by pixel gives me an error:

C#

int h, w;
h = pictureEdit1.Image.Height;
w = pictureEdit1.Image.Width;
Bitmap b = new Bitmap(h,w );


Bitmap p1 = (Bitmap )pictureEdit1.Image;
Bitmap p2 = (Bitmap)pictureEdit2.Image;
try
{
    for (int x = 0; x <= pictureEdit1.Image.Height; x++)
    {
        for (int i = 0; i <= pictureEdit1.Image.Width; i++)
        {

            if (p1.GetPixel(i, x) != p2.GetPixel(i,x))
            {
                 pictureEdit1.Image.Height.ToString());
                b.SetPixel(x, i, p2.GetPixel(x, i));

            }
            //else
            //{
            //    b.SetPixel(x, i, Color.Red);
            //}


        }
    }

}
catch (Exception ex)
{
    MessageBox.Show(ex.Message);
}
pictureEdit3.Image = b;

Exception Error
Parameter must be positive and < Height.
Parameter name: y

Posted 15-Feb-11 10:03am

Mostafa Elsadany

Updated 15-Feb-11 10:15am

v3

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Comments

DaveAuld 15-Feb-11 16:18pm

When using X,Y coords for points, why use x and i as you integers. use x and y and make things self documenting!

Manfred Rudolf Bihy 17-Feb-11 4:40am

I updated my answer to fix that your resulting image was rotated.

5 solutions

Solution 1

It seems you swapped up width and height there. You take picture1's height for the x axis and picture1's width for the y axis. It should be the other way. That was the most obvious thing there. There may or may not be other issues in your code - hard to say.

[Edit]
~~~~~~~~

Okay, even on top, you are creating a new Bitmap with the width-height swapped, so perhaps you intended it that way? The code is rather confusing.

Posted 15-Feb-11 10:17am

Nish Nishant

Updated 15-Feb-11 10:19am

v2

Comments

Manfred Rudolf Bihy 15-Feb-11 16:24pm

Actually he just got the naming wrong. Look again and see my answer :)

Nish Nishant 15-Feb-11 16:26pm

Possible, the code is written in a semi-obfuscated manner. :-)

Solution 2

I think it is your loops that are tripping you up.

Look at the outer loop, you have used <= and .Height +1

Look at the inner loop, you have used <= and .Width

They should both be treated the same.

I would think you would want to use < and .Height or .Width for both the loops.

Posted 15-Feb-11 10:17am

DaveAuld

Comments

Manfred Rudolf Bihy 15-Feb-11 16:22pm

Spotted the same as I did! 5+ :)

Solution 3

Man, you've got some strange stuff going on there.

Firstly, by convention use a variable 'x' to go across and 'y' to go up. Not 'i'.

The error looks like it comes about because you're going out of range on the height, looping here:

C#

for (int x = 0; x <= pictureEdit1.Image.Height+1; x++)

surely should be:

for (int y = 0; y < pictureEdit1.Image.Height; y++)

Still not sure what you want to do mind.

Also, the bitmap 'b' - width always comes before height - you're constucting it on its side...

Posted 15-Feb-11 10:17am

Rob Philpott

Updated 15-Feb-11 10:20am

v2

Comments

Manfred Rudolf Bihy 15-Feb-11 16:23pm

Well spotted! 5+

JF2015 17-Feb-11 4:46am

Very good answer. 5+

Solution 6

Hi,

If the two images are not the same size then your code will generate an exception

if (p1.GetPixel(i, x) != p2.GetPixel(i,x))

if i is bigger than the width of the second image than it breaks.

you should break out when then width is bigger then the second image width

Valery.

Posted 15-Feb-11 10:28am

Valery Possoz

Comments

Mostafa Elsadany 15-Feb-11 16:40pm

two image same size

Valery Possoz 15-Feb-11 16:46pm

Then look at Manfred's answer (#4):

for (int x = 0; x < pictureEdit1.Image.Height; x++)
{
for (int i = 0; i < pictureEdit1.Image.Width; i++)
{

That will solve your issue.

Mostafa Elsadany 15-Feb-11 17:14pm

thanks mann thanks for every

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Manfred Rudolf Bihy · Accepted Answer · 2011-02-15T10:21:00

It's in the condition of your for loops. See here:

C#

int h, w;
h = pictureEdit1.Image.Height;
w = pictureEdit1.Image.Width;
Bitmap b = new Bitmap(h,w );

Bitmap p1 = (Bitmap )pictureEdit1.Image;
Bitmap p2 = (Bitmap)pictureEdit2.Image;
try
{
    // Naming the loop variable for the vertical axis as X is completely idiotic
    // Besides that counting starts from zero so less than is the correct
    // comparison operator
    for (int x = 0; x < pictureEdit1.Image.Height; x++)
    {
        // Same argumentation as for the vertical axis. My comments also apply to the
        // horizontal axis (which should be named X)
        for (int i = 0; i < pictureEdit1.Image.Width; i++)
        {

            if (p1.GetPixel(i, x) != p2.GetPixel(i,x))
            {
                pictureEdit1.Image.Height.ToString());
                // The following line is your faulty rotating code
                // b.SetPixel(x, i, p2.GetPixel(x, i));
                // The next line fixes the rotating of the created image
                b.SetPixel(i, x, p2.GetPixel(i, x));
            }
            //else
            //{
            // Same error here
            //    b.SetPixel(x, i, Color.Red);
            // Should be :
            //    b.SetPixel(i, x, Color.Red);
            //}
        }
    }

}
catch (Exception ex)
{
    MessageBox.Show(ex.Message);
}
pictureEdit3.Image = b;

Best Regards,
Manfred

Help in subtraction of two images

5 solutions

Solution 1

Solution 2

Solution 3

Solution 5

Solution 6

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