For the benefit of anyone else finding themselves here. The solution outlined here worked for me:
http://gamedev.stackexchange.com/questions/53638/android-loading-bitmaps-without-premultiplied-alpha-opengl-es-2-0 My actual implementation differs slightly from the description on gamedev because I was already multiplying the texture color by two different variable color vectors (one for the *sprite* and another global color). Because of this I ended up passing separate *alpha* value to the shader(s) and forcing the alpha value on the variable colors to 1.0f. In the end, my fragment shader looks like this: varying float v_Alpha; // Independent alpha value to account for premultiplied alpha values in PNG files ... gl_FragColor = texture2D(u_Texture, v_TexCoordinate) * u_Color * v_Color * v_Alpha; u_Color is a uniform color, v_Color is variable (for the sprite) and v_Alpha is the single float value for alpha. This means I can use: GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE_MINUS_SRC_ALPHA); Which accounts for the premultiplied alpha values in the PNG. The upshot is I can continue to use the BitmapFactory to load the textures. I can't be sure, but I suspect the artifacts I was seeing were as result of NOT using pre-multiplied alpha textures. Still not sure what the blur on the textures was caused by when using GL_CLAMP_TO_EDGE :/ Peace out. On Monday, September 2, 2013 6:45:23 PM UTC-7, Jason wrote: > > P.S. It turns out the *blur* is from using GL_CLAMP_TO_EDGE. Changing > to GL_REPEAT removes the blur even though it doesn't really make sense to > repeat the texture as I'm just rendering sprites as quads (triangle pairs). > > On Monday, September 2, 2013 6:29:17 PM UTC-7, Jason wrote: >> >> >> On Monday, September 2, 2013 6:23:43 PM UTC-7, Jason wrote: >>> >>> I realize this is an old thread, but I'm having the same issue and the >>> above solutions haven't worked for me. >>> >>> Firstly the link to the PNGDecoder from libgdx is old and no longer >>> exists (libgdx appear to have re-vamped the way they load images and >>> tracking down where exactly the PNG decoding happens is a bit of a >>> nightmare) >>> >>> I tried directly calling GLES20.glTexImage2D using the pixels extracted >>> from the Bitmap (as described above), but I still get gray artifacts on the >>> edges of the texture. >>> >>> For example: >>> >>> The top image is the original PNG, the bottom is after rendering (taken >>> from screenshot) >>> >>> >>> <https://lh6.googleusercontent.com/-Dyf568n0gD4/UiU4vJP80wI/AAAAAAAACsY/ygEOOrLYBao/s1600/cloud_text_problem.png> >>> >>> The bottom image has gray pixel artifacts around the edge. It's also >>> sort of *blurry* which I can't work out either. >>> >>> I tried manually decoding the PNG using this: >>> >>> http://wiki.l33tlabs.org/bin/view/TWL/Using+the+TWL+PNGDecoder >>> >>> But got the same result. >>> >>> I'm creating the texture with: >>> >>> GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, >>> GLES20.GL_TEXTURE_MIN_FILTER, GLES20.GL_LINEAR); >>> GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, >>> GLES20.GL_TEXTURE_MAG_FILTER, GLES20.GL_LINEAR); >>> GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_S, >>> GLES20.GL_CLAMP_TO_EDGE); >>> GLES20.glTexParameteri(GLES20.GL_TEXTURE_2D, GLES20.GL_TEXTURE_WRAP_T, >>> GLES20.GL_CLAMP_TO_EDGE); >>> >>> My fragment shader is pretty basic, just multiplies the texture color by >>> a couple of other color values I pass in: >>> >>> gl_FragColor = texture2D(u_Texture, v_TexCoordinate) * u_Color * v_Color; >>> >>> Does anyone have a clue as to: >>> >>> 1) How I can render/create the texture without the artifacts >>> 2) Why the texture is kind of blurry once it's rendered. >>> >>> Thanks! >>> >>> >>> On Sunday, September 2, 2012 11:43:59 AM UTC-7, arberg wrote: >>>> >>>> Hi, >>>> >>>> I think it would make sense that either Bitmap could be without >>>> premultiplied alpha, or GLUtils.texImage2D method could take as parameter >>>> whether to load with or without premultiplied alpha. Since you say Bitmaps >>>> will never be without premultiplied alpa, I suggest the latter, plus as >>>> you >>>> suggest a convenience method on the Bitmap, which returns its content in >>>> an >>>> array without premultiplied alpha. >>>> >>>> It makes sense to me to add the option to GLUtils.texImage2D since the >>>> very purpose of the GLUtils class is '... to help bridging OpenGL ES and >>>> Android APIs.' (javadoc class reference). >>>> >>>> Cheers Alex >>>> >>>> On Friday, 29 June 2012 21:18:59 UTC+2, Romain Guy (Google) wrote: >>>>> >>>>> Another big issue similar to alpha-premultiply is that 32Bit ARGB >>>>>> Images are changed >>>>>> to 16Bit after scaling (especially if all alpha values are 255), >>>>>> without some dirty tricks. >>>>>> This is a big issue to, it's far away from the precission needed for >>>>>> good normal mapping. >>>>>> >>>>> >>>>> There was a bug in the scaling code that I fixed. a 32 bits image will >>>>> now always be scaled to another 32 bits image. >>>>> >>>>> >>>>>> >>>>>> -- >>>>> Romain Guy >>>>> Android framework engineer >>>>> [email protected] >>>>> >>>>> -- You received this message because you are subscribed to the Google Groups "Android Developers" group. 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