Harshini Madurapperuma wrote:
Is there a way to add a background image to AWT preview?
I don't know anything about FOP's AWT features, but if you can get the rendered preview as a bitmap, you can generate a composite with a very simple image processing algorithm called a multiply. (If you have Photoshop, you can try this out before you start coding: it's one of the layer blend modes.)
It works like this: For each pixel, get its luminance as a value from 0 to 1 (darkest to brightest) and multiply the two together. Then, modify the background's luminance with the new value. Where the FOP output is white (the "paper"), nothing will happen to the background because 1 times x is x. Where there is text, the background will be obliterated, since 0 times x is 0. If FOP generates any grays (such as for antialiasing) they will simply darken the background proportionately to the brightness of the gray.
This will work best if the document has no color, only shades of gray. There is no such restriction on the background.
If AWT doesn't have a way to get a luminosity for a pixel, look up RGB to HSB conversion on the web. Don't use an RGB to HSL algorithm: HSL is a more complex color space than HSB, with no benefit here. The luminosity ("brightness") in HSB goes from 0 to 1, just as we want here, but in HSL it goes from -1 to +1. The HSL <-> RGB conversions are also harder to calculate correctly than HSB <-> RGB.
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