Alpha value is not working in BITMAP

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I have the pixel array containing the RGBA (RGB and Alpha) values consequently. I want to apply the alpha value for each pixel. For that I am using BITMAPV4HEADER and 'SetDIBitsToDevice' function to draw the pixel array into picture box. But the Alpha value is not working (RGB is working fine). How can i use alpha value??

I am tried with AlphaBlend function, but it always apply the transparency to all pixels. I want apply for each pixel with different alpha value by using(SetDIBitsToDevice).

Posted 3-Jun-13 2:11am

Rajeshkumar Ramasamy

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Matthew Faithfull 3-Jun-13 8:56am

I can't find anything in the documentation for SetDIBitsToDevice that indicates it uses alpha values. What makes you think this should work?

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Jochen Arndt · Accepted Answer · 2013-06-03T02:51:00

Solution 1

As already noted in a reply to your previous question, GDI functions like SetDIBitsToDevice will clear the alpha values of the bitmap. See Alpha Blending a Bitmap[^] in the MSDN on how to use the AlphaBlend function with source alpha values.

Posted 3-Jun-13 2:51am

Jochen Arndt

nv3 · Accepted Answer · 2013-06-03T02:53:00

Solution 2

The documentation of AlphaBlend says to set bSrcAlpha to 255 to use the per-pixel alpha values. Have you done that?

Posted 3-Jun-13 2:53am

nv3

Comments

Rajeshkumar Ramasamy 5-Jun-13 7:11am

I got it :-)

nv3 5-Jun-13 7:37am

You are welcome!