ImageEn Forum - masking out parts of an image

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ImageEn Library for Delphi, C++ and .Net

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masking out parts of an image

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tcardinal

27 Posts

Posted - May 25 2012 : 09:28:29

I am sure that this is fairly straighforward but can't see it in the help file.

I have 2 images one in colour and one in black and white. I want to use the black and white image to remove parts from the colour image. Think of teh black and white image as a checker board and when applied to the colour image the colour image keeps all the parts overlayed by a black square and removes all the parts covered with a white square and replaces then with a solid colour or makes them transparent.

Thanks

Russell

fab

1310 Posts

Posted - May 28 2012 : 14:41:31

You can load the alpha channel from an external file (assuming it has the same width and height of current image) with:

ImageEnView1.IO.LoadFromFile('mainimage.jpg');
ImageEnView1.AlphaChannel.Read('alphachannel.jpg');
ImageEnVIew1.AlphaChannel.PixelFormat := ie8g;
ImageEnView1.Update();

Now areas with "0" in alphachannel.jpg are transparent.
If you want to fill transparent areas with a color (hence to discard alpha channel), you can execute:

// fill transparent areas with red (255,0,0)
ImageEnView1.SetAlphaRangePixelsColor(0, 0, CreateRGB(255, 0, 0));
ImageEnView1.RemoveAlphaChannel();

Hope this helps.

tcardinal

27 Posts

Posted - May 29 2012 : 01:51:31

Thanks, I'll give it a go

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