Scale alpha masked sprite aura problem
Blitz3D Forums/Blitz3D Programming/Scale alpha masked sprite aura problem
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| Hello, I am rescaling an alhpa masked sprite and the sprite appears to have a white "aura" around it which gets increasingly noticeable as the sprite grows. I have tried both using alpha antialised pixels around rounded edges of the sprite as well as "solid and 100% transparent areas" too. The background is dark, and the edges around the sprite is back too so I don't know what is causing the bright outline. Any ideas? I have tried both 24bit PNG with transparency as well as TGA. Thanx Stefan |
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| It sounds like your pixels are transparent white (0x00ffffff) instead of transparent black (0x00000000). For best results you want to use the transparent version of any neighboring solid pixels. |
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| Where do I set that, in B3D or when I save the image? (I have only used BPlus and B2 before, so I am new to this, testing some 3D stuff to "rest my eyes" from CTCC at times =) Thanks |
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| In PhotoShop check your R, G and B channels. If you want to process it in Blitz, use If (ReadPixel(x,y) and 0xff000000)=0 WritePixel(x,y,0). |
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| I'm trying to follow u on this one, but I'll post these images first to make sure we're talking about the same thing. Here is what the test image looks like as a rescaled sprite with a background:  ...here is a zoomed in look at how the alpha is in photoshop:  And here is the PSD file if anything else in terms of transparency needs to be verified: http://www.imphenzia.com/temp/p1_c.psd Would this lead to the problem that you are describing? I thought alpha was just alpha, i.e. how visible should this pixel be with the color values R G B. Thanks again |
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| When graphics hardware multisamples pixels for scaling it does the 4 channels RGBA separately so even if Alpha=0 the RGB from transparent pixels impacts on edge colors. Photoshop doesn't seem to allow setting of transparent color to anything but white so you need to either start working with 4 channel images or process the images once loaded with that readpixel/writepixel method I explained above. |
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| Maybe you only need to turn off antialias mode in the blending of the pasted Graphics? But anyway: I would work with 32 Bit TGAs in Photoshop - at least in Version 6. |
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| Thanks for the replies I managed to use the approach that skidracer mentioned with converting it to "black" alpha values. Strangely enough the regions with 100% opacity turned white then?? But I worked around that too by using a black background, and not the fully transparent photoshop option (if that makes any sense). |
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