alphablending

I'm having a really hard time working with some source images in PNG format that have premultiplied alpha because most tools simply do not support it correctly. Is there anything out there that can do a "best guess" conversion to a more conventional PNG? If by "premultiplied alpha" you mean iOS's PNG derivative, then you can convert them back to PNGs with pngdefry . Standard PNGs never use premultiplied alpha. 来源： https://stackoverflow.com/questions/7189417/convert-png-from-premultiplied-alpha-to-conventional-alpha-transparancy

I have a problem with incorrect alpha blending results with openGL ES on iPhone. This is my code for creating texture object: glGenTextures(1, &tex_name); glBindTexture(GL_TEXTURE_2D, tex_name); glTextImage2D(GL_TEXTURE_2D, 0, GL_RGBA, tex_width, tex_height, GL_RGBA, GL_UNSIGNED_BYTE, tex_data); 'tex_data' is loaded from raw RGBA8888 data packed with zlib. It loads as it should, wich i've checked with a debugger. This is my code for setting up texture before rendering: glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glBindTexture(GL_TEXTURE_2D, tex_name); glTexParameteri

I have a somewhat transparent view (alpha = 0.6) that has some subviews. I'd like one of the subviews (a UILabel) to be drawn with alpha of 1.0 because the blending makes the text difficult to read but by adding it as a subview of the main view it has adopted its parent's alpha value. Is there a way to override this behavior? I believe I'll have to remove it from the subview but wanted to ask and see if maybe I'm missing something. You are correct. You'll have to move the UILabel out of the transparent view to get it to render as non-transparent. Brian is right. For example : view

I want to draw transparent windows (with alpha channel) on Linux (GTK) and OSX. Is there an API to do that ? Note that I don't want to set a global transparency, the alpha level should be set per pixel. I'm looking for the same kind of API than the UpdateLayeredWindow function on Windows, as in this example: Per Pixel Alpha Blend . For Mac OS X, see the RoundTransparentWindow sample code. It works by using a custom completely transparent window and drawing shapes in it. Although the example only uses shapes with hard edges + overall alpha, arbitrary alpha can be used. Although the example uses

I have made a lookup table that allows you to blend two single-byte channels (256 colors per channel) using a single-byte alpha channel using no floating point values (hence no float to int conversions). Each index in the lookup table corresponds to the value of 256ths of a channel, as related to an alpha value. In all, to fully calculate a 3-channel RGB blend, it would require two lookups into the array per channel, plus an addition. This is a total of 6 lookups and 3 additions. In the example below, I split the colors into separate values for ease of demonstration. This example shows how to