Image operations

[timmy013]

Hi,

I have a few transparent .png images with same size and want to add or subtract them one of other and then put the image to picturebox.

First picture:


Second picture which contains white pixels (or it could be black pixels) which should be erased from first picture:


The result should look like this:


Is there any way to this fast, but not looping through pixels? BitBlt using?
Some code example, please.

Thanks

 

[timmy013]

I have managed to solve this problem, but had to make some changes.

Second picture, which used to be white mask - have to be changed to be consisted of pixels that are in color that don't exist on source picture. So, I have change the mask picture - white pixels are changed to HotPink pixels


This code will do what I need

1. Copy mask image over source
2. Make transparent all HotPink pixels

        Dim g As Graphics
        Dim b_mask As New Bitmap(mask.Image)
        Dim b_original As New Bitmap(src.Image)
        g = Graphics.FromImage(b_original)
        g.DrawImage(b_mask, New Point(0, 0))
        b_original.MakeTransparent(Color.HotPink)
        src.Image = b_original

This works fine, but what if there are some HotPink pixels on the original before applying the mask?
Solution could be to shift the mask pixel color using ColorMatrix and ImageAttributes, but how to be sure that new pixel color doesn't exist on original image?

Of course, looping through pixels is not what I want to do because of speed issue.