PNG alpha channel help

Blitz3D Forums/Blitz3D Programming/PNG alpha channel help

Qube (Posted 2005) [#1]

I know this has come up many times before, but for the life of me I can't find any info on it. Say I have a simple filled circle image, using a drop shadow in photoshop. I save the image as PNG. How do I place these images in Blitz3D next to each other retaining the alpha channel? Lol, it's doing my head in. I know I'm missing something really simple here.

jfk EO-11110 (Posted 2005) [#2]

On the Photoshop side you probably need to create an additional Layer. after R,G and B this will be Alpha by default. If you save it now, I guess it will save the PNG (if memory serves :) ). On the blitz side note images cannot use transparency info. all they can utilize is a mask color. It's black by default, but it may be altered to use an other color (MaskImage, IIRC) Alpha Channels can only be used by textures. You may use a system that positions Sprites or Quads side by side to get the effect of images that are supporting smooth alpha transparency.

Qube (Posted 2005) [#3]

Thanks :) Damnit!!! I thought there was a technique which allowed PNG images to use their alpha channel via drawimage?. Ah well, not to worry, I'll just have to tone down certain areas.

Shifty Geezer (Posted 2005) [#4]

All depends on the software. In PSP you can save the png and (being sure to save as True Colour, not 256 colour) choose "Transparency : use current transparency". No need to setup an alpha channel - WYSIWYG!

Damien Sturdy (Posted 2005) [#5]

Shifty. yes. but, it still wont work with DrawImage ;)

Shifty Geezer (Posted 2005) [#6]

Sorry, wasn't paying attention!

IPete2 (Posted 2005) [#7]

er... you could load them as sprites or textures though (for a quad for example) and use the flags set to 3 to keep alpha info. It would be one image not two separate images though. This would work - try it : www.smartscreenuk.com/circle.png (although this is a none filled circle). IPete2.

Qube (Posted 2005) [#8]

Well textures are out because some of the people who'll be using the proggy are still using voodoo III's and I remember correctly those cards don't support above 256kb textures. My best bet is to skip using any fancy shading and alpha windows for this project.