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#1 Posted : Wednesday, November 25, 2009 9:29:27 PM(UTC)

Groups: Registered
Posts: 1


I have a PNG image with an alpha channel - this alpha channel is used to imitate a nice drop shadow on what ever background the PNG is shown on.

Currently I use LEADTOOLS (.NET) to resize the PNG.
Now I would like to flatten the image in the process and save it as a JPEG. White must be used as the background - so the shadiw must be cast on the white background.
How would you do that ?

Kind regards


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#2 Posted : Monday, November 30, 2009 7:10:13 AM(UTC)


Groups: Tech Support
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Hello Mikkel,

In order to combine the Alpha channel data with the image data, you'll have to use either the AlphaBlendCommand or the FeatherAlphaBlend command to flatten the images together. These are both in the Leadtools.ImageProcessing.Effects namespace.

If you're loading the PNG from file with the alpha data, you'll need to specifically indicate to the RasterCodecs engine to load the extra alpha data with the raster image by specifying the higher bit depth.

You can use the RasterImage.CreateAlphaImage() method to create an image out of the alpha data to combine with the above methods.

There is an example in our help files illustrating how to use the aforementioned methods.
Walter Bates
Senior Support Engineer
LEAD Technologies, Inc.
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