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2014/10/15 ¤U¤È 10:05:00
iphone Programming Glossary: cgbitmapcontextRetrieving a pixel alpha value for a UIImage http://stackoverflow.com/questions/1042830/retrieving-a-pixel-alpha-value-for-a-uiimage height width 4 bytesPerPixel 4 bytesPerRow bytesPerPixel width NSUInteger bitsPerComponent 8 CGContextRef context CGBitmapContextCreate rawData width height bitsPerComponent bytesPerRow colorSpace kCGImageAlphaPremultipliedLast kCGBitmapByteOrder32Big.. kCGBlendModeCopy Edit after thinking You could do the lookup much more efficient by building the smallest possible CGBitmapContext 1x1 pixel maybe 8x8 have a try and translating the context to your desired position before drawing CGContextTranslateCTM..
OpenGL ES; rendering texture created from CGBitmapContext http://stackoverflow.com/questions/2713890/opengl-es-rendering-texture-created-from-cgbitmapcontext ES rendering texture created from CGBitmapContext I am executing the following which I have derived from a few different tutorials Just a single render pass initialisation.. int height 50 void textureData malloc width height 4 CGColorSpaceRef cSp CGColorSpaceCreateDeviceRGB CGContextRef ct CGBitmapContextCreate textureData width height 8 width 4 cSp kCGImageAlphaPremultipliedLast kCGBitmapByteOrder32Big CGContextSetRGBFillColor..
http://stackoverflow.com/questions/3231690/inner-shadow-in-uilabel masked differently. If you need it on an older version of iOS you would have to replace the block and use an annoying CGBitmapContext. UIImage blackSquareOfSize CGSize size UIGraphicsBeginImageContextWithOptions size NO 0 UIColor blackColor setFill CGContextFillRect..
clipping a UIImage as per a polygon http://stackoverflow.com/questions/3667939/clipping-a-uiimage-as-per-a-polygon the DrawRect method of your view. If you actually want to have the clipped image data the context would probably be a CGBitmapContext something like this CGColorSpaceRef colorSpace CGColorSpaceCreateDeviceGray size_t bytesPerPixel 1 size_t bytesPerRow bmpWidth.. bytesPerRow bmpHeight unsigned char bmpData malloc bmpDataSize memset bmpData 0 bmpDataSize CGContextRef bmpCtx CGBitmapContextCreate bmpData bmpWidth bmpHeight 8 bytesPerRow colorSpace kCGImageAlphaNone kCGBitmapByteOrderDefault the code example is..
Create a UIImage by rendering UIWebView on a background thread - iPhone http://stackoverflow.com/questions/4660999/create-a-uiimage-by-rendering-uiwebview-on-a-background-thread-iphone the webView's layer to the UIGraphicalContext but the _WebTryThreadLock error crashed the webviews. I tried creating a CGBitmapContext and render the webview's layer to it but got the same result. I tried implementing a copy method by adding a Category to..
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 to pull out the ARGB component from BitmapContext on iPhone I'm trying to get ARGB components from CGBitmapContext with the following codes id initWithImage UIImage image create BitmapContext with UIImage and use 'pixelData' as the pointer.. CGColorSpaceCreateDeviceRGB pixelData malloc bitmapByteCount unsigned char pixelData is defined in head file context CGBitmapContextCreate pixelData image.size.width image.size.height 8 bits per component bitmapBytesPerRow colorSpace kCGImageAlphaPremultipliedFirst.. colorSpace CGContextDrawImage context CGRectMake 0 0 image.size.width image.size.height image.CGImage pixelData CGBitmapContextGetData context return self float alphaAtX int x y int y get alpha component using the pointer 'pixelData' return pixelData..
How to implement alpha gradient on a image? http://stackoverflow.com/questions/5908731/how-to-implement-alpha-gradient-on-a-image a masking image to it. You could generate an appropriate mask simply enough by drawing to a greyscale or alpha only CGBitmapContext with CGContextDrawLinearGradient . If it's being displayed as the content of a CALayer you could apply an appropriate masking.. property. You could use a CAGradientLayer with appropriate colors to create this mask. You can draw the image to a CGBitmapContext and then draw an appropriate alpha gradient over it using kCGBlendModeDestinationIn . Or draw the gradient first and draw.. both cases CGContextDrawLinearGradient is again your friend. Then of course get the image out of the CGContext using CGBitmapContextCreateImage or CGImageCreate on the underlying data buffer. Or of course if you control the original image and never need..
OpenGL ES 2.0 / MonoTouch: Texture is colorized red http://stackoverflow.com/questions/7986153/opengl-es-2-0-monotouch-texture-is-colorized-red Int32 image.Size.Width Int32 image.Size.Height 0 All.Rgba All.UnsignedByte RequestImagePixelData image protected CGBitmapContext CreateARGBBitmapContext CGImage inImage var pixelsWide inImage.Width var pixelsHigh inImage.Height var bitmapBytesPerRow.. bitmapByteCount if bitmapData IntPtr.Zero throw new Exception Memory not allocated. var context new CGBitmapContext bitmapData pixelsWide pixelsHigh 8 bitmapBytesPerRow colorSpace CGImageAlphaInfo.PremultipliedFirst if context null throw.. Store pixel data as an ARGB Bitmap protected IntPtr RequestImagePixelData UIImage inImage var imageSize inImage.Size CGBitmapContext ctxt CreateARGBBitmapContext inImage.CGImage var rect new RectangleF 0.0f 0.0f imageSize.Width imageSize.Height ctxt.DrawImage..
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