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2014/10/15 ¤U¤È 10:12:51

iphone Programming Glossary: premultiplied

Retrieving a pixel alpha value for a UIImage

http://stackoverflow.com/questions/1042830/retrieving-a-pixel-alpha-value-for-a-uiimage

in a UIImageView. I have obtained the CGImage from UIImageView image and created a RGBA byte array from this. Alpha is premultiplied. CGImageRef image uiImage.CGImage NSUInteger width CGImageGetWidth image NSUInteger height CGImageGetHeight image CGColorSpaceRef.. need to translate the co ordinates between UIKit and Core Graphics i.e is the y axis inverted Or have I misunderstood premultiplied alpha values Update @Nikolai Ruhe's suggestion was key to this. I did not in fact need to translate between UIKit coordinates..

Alternatives to creating an openGL texture from a captured video frame to overlay an openGL view over video? (iPhone)

http://stackoverflow.com/questions/4473894/alternatives-to-creating-an-opengl-texture-from-a-captured-video-frame-to-overla

object is blended on top of layers underneath it in the layer hierarchy the renderbuffer ™s color data must be in a premultiplied alpha format to be composited correctly by Core Animation. Blending OpenGL ES content on top of other content has a severe..

How to pull out the ARGB component from BitmapContext on iPhone?

http://stackoverflow.com/questions/561663/how-to-pull-out-the-argb-component-from-bitmapcontext-on-iphone

RGBA not ARGB use it as such in the creation of your context or adapt the alphaAtX code. I'm not sure if you want premultiplied if it's just to check alpha values you don't. All in all something like ... CGContextRelease context context CGBitmapContextCreate..

Is programmatically inverting the colors of an image possible?

http://stackoverflow.com/questions/6672517/is-programmatically-inverting-the-colors-of-an-image-possible

memoryPool y width 4 step through the pixels one by one... for int x 0 x width x get RGB values. We're dealing with premultiplied alpha here so we need to divide by the alpha channel if it isn't zero of course to get uninflected RGB. We multiply by.. bitmap context that it can access the memory of draws the UIImage to it runs through every pixel converting from premultiplied alpha to uninflected RGB inverting each channel separately multiplying by alpha again and storing back gets an image from..

Save OpenGL Drawn item as a Image

http://stackoverflow.com/questions/9660723/save-opengl-drawn-item-as-a-image

glEnable GL_TEXTURE_2D glEnableClientState GL_VERTEX_ARRAY glEnable GL_BLEND Set a blending function appropriate for premultiplied alpha pixel data glBlendFunc GL_ONE GL_ONE_MINUS_SRC_ALPHA glEnable GL_POINT_SPRITE_OES glTexEnvf GL_POINT_SPRITE_OES GL_COORD_REPLACE_OES..

Record the drawing as a m4v video file - OpenGL

http://stackoverflow.com/questions/9661259/record-the-drawing-as-a-m4v-video-file-opengl

glEnable GL_TEXTURE_2D glEnableClientState GL_VERTEX_ARRAY glEnable GL_BLEND Set a blending function appropriate for premultiplied alpha pixel data glBlendFunc GL_ONE GL_ONE_MINUS_SRC_ALPHA glEnable GL_POINT_SPRITE_OES glTexEnvf GL_POINT_SPRITE_OES GL_COORD_REPLACE_OES..