DSP上的UIImage

Question

可能重複：
How to get pixel data from a UIImage (Cocoa Touch) or CGImage (Core Graphics)?

比方說，我有一個UIImage，我想獲得的RGB矩陣，以做一些關於它的處理，不要更改它，只需獲取UIImage數據，以便我可以使用我的C算法就可以了。你可能知道，所有的數學都是在圖像rgb矩陣上完成的。

Answer 1

基本步驟是創建一個位圖上下文CGBitmapContextCreate，然後將您的圖像繪製到該上下文中並獲取CGBitmapContextGetData的內部數據。這裏有一個例子：

UIImage *image = [UIImage imageNamed:@"MyImage.png"]; 

//Create the bitmap context: 
CGImageRef cgImage = [image CGImage]; 
size_t width = CGImageGetWidth(cgImage); 
size_t height = CGImageGetHeight(cgImage); 
size_t bitsPerComponent = 8; 
size_t bytesPerRow = width * 4; 
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 
CGContextRef context = CGBitmapContextCreate(NULL, width, height, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast); 
//Draw your image into the context: 
CGContextDrawImage(context, CGRectMake(0, 0, width, height), cgImage); 
//Get the raw image data: 
unsigned char *data = CGBitmapContextGetData(context); 

//Example how to access pixel values: 
size_t x = 0; 
size_t y = 0; 
size_t i = y * bytesPerRow + x * 4; 
unsigned char redValue = data[i]; 
unsigned char greenValue = data[i + 1]; 
unsigned char blueValue = data[i + 2]; 
unsigned char alphaValue = data[i + 3]; 
NSLog(@"RGBA at (%i, %i): %i, %i, %i, %i", x, y, redValue, greenValue, blueValue, alphaValue); 

//Clean up: 
CGColorSpaceRelease(colorSpace); 
CGContextRelease(context); 
//At this point, your data pointer becomes invalid, you would have to allocate 
//your own buffer instead of passing NULL to avoid this.