2014/10/15 下午 10:04:48

iphone Programming Glossary: byteindex

Retrieving a pixel alpha value for a UIImage

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

the array index for the given alpha channel using the coordinates from the UIImageView. int byteIndex bytesPerRow uiViewPoint.y uiViewPoint.x bytesPerPixel unsigned char alpha rawData byteIndex 3 However.. int byteIndex bytesPerRow uiViewPoint.y uiViewPoint.x bytesPerPixel unsigned char alpha rawData byteIndex 3 However I don't get the values I expect. For a completely black transparent area of the image I get..

Convert image to grayscale

http://stackoverflow.com/questions/1298867/convert-image-to-grayscale

0 xCoordinate width xCoordinate for int yCoordinate 0 yCoordinate height yCoordinate int byteIndex bytesPerRow yCoordinate xCoordinate bytesPerPixel Getting original colors float red rawData byteIndex.. bytesPerRow yCoordinate xCoordinate bytesPerPixel Getting original colors float red rawData byteIndex 255.f float green rawData byteIndex 1 255.f float blue rawData byteIndex 2 255.f Processing pixel data.. bytesPerPixel Getting original colors float red rawData byteIndex 255.f float green rawData byteIndex 1 255.f float blue rawData byteIndex 2 255.f Processing pixel data float averageColor red green blue..

Retrieving a pixel alpha value for a UIImage

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

0 0 width height image CGContextRelease context I then calculate the array index for the given alpha channel using the coordinates from the UIImageView. int byteIndex bytesPerRow uiViewPoint.y uiViewPoint.x bytesPerPixel unsigned char alpha rawData byteIndex 3 However I don't get the values I expect. For a completely black transparent.. alpha channel using the coordinates from the UIImageView. int byteIndex bytesPerRow uiViewPoint.y uiViewPoint.x bytesPerPixel unsigned char alpha rawData byteIndex 3 However I don't get the values I expect. For a completely black transparent area of the image I get non zero values for the alpha channel. Do I need to translate..

Convert image to grayscale

http://stackoverflow.com/questions/1298867/convert-image-to-grayscale

NSUInteger bytesPerRow bytesPerPixel width for int xCoordinate 0 xCoordinate width xCoordinate for int yCoordinate 0 yCoordinate height yCoordinate int byteIndex bytesPerRow yCoordinate xCoordinate bytesPerPixel Getting original colors float red rawData byteIndex 255.f float green rawData byteIndex 1 255.f float blue rawData.. int yCoordinate 0 yCoordinate height yCoordinate int byteIndex bytesPerRow yCoordinate xCoordinate bytesPerPixel Getting original colors float red rawData byteIndex 255.f float green rawData byteIndex 1 255.f float blue rawData byteIndex 2 255.f Processing pixel data float averageColor red green blue 3.0f red averageColor green.. yCoordinate int byteIndex bytesPerRow yCoordinate xCoordinate bytesPerPixel Getting original colors float red rawData byteIndex 255.f float green rawData byteIndex 1 255.f float blue rawData byteIndex 2 255.f Processing pixel data float averageColor red green blue 3.0f red averageColor green averageColor blue averageColor..

Retrieving a pixel alpha value for a UIImage

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

context I then calculate the array index for the given alpha channel using the coordinates from the UIImageView. int byteIndex bytesPerRow uiViewPoint.y uiViewPoint.x bytesPerPixel unsigned char alpha rawData byteIndex 3 However I don't get the values.. from the UIImageView. int byteIndex bytesPerRow uiViewPoint.y uiViewPoint.x bytesPerPixel unsigned char alpha rawData byteIndex 3 However I don't get the values I expect. For a completely black transparent area of the image I get non zero values for..

Convert image to grayscale

http://stackoverflow.com/questions/1298867/convert-image-to-grayscale

width for int xCoordinate 0 xCoordinate width xCoordinate for int yCoordinate 0 yCoordinate height yCoordinate int byteIndex bytesPerRow yCoordinate xCoordinate bytesPerPixel Getting original colors float red rawData byteIndex 255.f float green.. yCoordinate int byteIndex bytesPerRow yCoordinate xCoordinate bytesPerPixel Getting original colors float red rawData byteIndex 255.f float green rawData byteIndex 1 255.f float blue rawData byteIndex 2 255.f Processing pixel data float averageColor.. yCoordinate xCoordinate bytesPerPixel Getting original colors float red rawData byteIndex 255.f float green rawData byteIndex 1 255.f float blue rawData byteIndex 2 255.f Processing pixel data float averageColor red green blue 3.0f red averageColor..

Create a mask from difference between two images (iPhone)

http://stackoverflow.com/questions/3901404/create-a-mask-from-difference-between-two-images-iphone

height imageRef CGContextRelease context Now your rawData contains the image data in the RGBA8888 pixel format. int byteIndex bytesPerRow yy xx bytesPerPixel for int ii 0 ii count ii CGFloat red rawData byteIndex 1.0 255.0 CGFloat green rawData.. the RGBA8888 pixel format. int byteIndex bytesPerRow yy xx bytesPerPixel for int ii 0 ii count ii CGFloat red rawData byteIndex 1.0 255.0 CGFloat green rawData byteIndex 1 1.0 255.0 CGFloat blue rawData byteIndex 2 1.0 255.0 CGFloat alpha rawData byteIndex.. yy xx bytesPerPixel for int ii 0 ii count ii CGFloat red rawData byteIndex 1.0 255.0 CGFloat green rawData byteIndex 1 1.0 255.0 CGFloat blue rawData byteIndex 2 1.0 255.0 CGFloat alpha rawData byteIndex 3 1.0 255.0 byteIndex 4 UIColor acolor..

Filling a portion of an image with color

http://stackoverflow.com/questions/8124308/filling-a-portion-of-an-image-with-color