最近看这个比较多人用到,以前有使用过,现在,粘过来给大伙看看.

注意:UIImageView的大小只能跟图片一样大.要不然取色不对.

- (UIColor *) getPixelColorAtLocation:(CGPoint)point {
           UIColor* color = nil;         CGImageRef inImage = self.image.CGImage; // Create off screen bitmap context to draw the image into. Format ARGB is 4 bytes for each pixel: Alpa, Red, Green, Blue         CGContextRef cgctx = [self createARGBBitmapContextFromImage:inImage]; if (cgctx == NULL) {
   return nil; /* error */         }     size_t w = CGImageGetWidth(inImage);         size_t h = CGImageGetHeight(inImage);         CGRect rect = {
   {
   0,0},{w,h}}; // Draw the image to the bitmap context. Once we draw, the memory // allocated for the context for rendering will then contain the // raw image data in the specified color space.         CGContextDrawImage(cgctx, rect, inImage); // Now we can get a pointer to the image data associated with the bitmap // context.         unsigned char* data = CGBitmapContextGetData (cgctx); if (data != NULL) {
   //offset locates the pixel in the data from x,y. //4 for 4 bytes of data per pixel, w is width of one row of data.                 int offset = 4*((w*round(point.y))+round(point.x)); int alpha =  data[offset]; int red = data[offset+1]; int green = data[offset+2]; int blue = data[offset+3]; //NSLog(@"offset: %i colors: RGB A %i %i %i  %i",offset,red,green,blue,alpha);                 color = [UIColor colorWithRed:(red/255.0f) green:(green/255.0f) blue:(blue/255.0f) alpha:(alpha/255.0f)];         } // When finished, release the context         CGContextRelease(cgctx); // Free image data memory for the context         if (data) { free(data); } return color; } - (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {
           CGContextRef    context = NULL;         CGColorSpaceRef colorSpace; void *          bitmapData; int             bitmapByteCount; int             bitmapBytesPerRow; // Get image width, height. We'll use the entire image.         size_t pixelsWide = CGImageGetWidth(inImage);         size_t pixelsHigh = CGImageGetHeight(inImage); // Declare the number of bytes per row. Each pixel in the bitmap in this // example is represented by 4 bytes; 8 bits each of red, green, blue, and // alpha.         bitmapBytesPerRow   = (pixelsWide * 4);         bitmapByteCount     = (bitmapBytesPerRow * pixelsHigh); // Use the generic RGB color space.         colorSpace = CGColorSpaceCreateDeviceRGB(); if (colorSpace == NULL)         {
                   fprintf(stderr, "Error allocating color space\n"); return NULL;         } // Allocate memory for image data. This is the destination in memory // where any drawing to the bitmap context will be rendered.         bitmapData = malloc( bitmapByteCount ); if (bitmapData == NULL)         {
                   fprintf (stderr, "Memory not allocated!");                 CGColorSpaceRelease( colorSpace ); return NULL;         } // Create the bitmap context. We want pre-multiplied ARGB, 8-bits // per component. Regardless of what the source image format is // (CMYK, Grayscale, and so on) it will be converted over to the format // specified here by CGBitmapContextCreate.         context = CGBitmapContextCreate (bitmapData,                                                                          pixelsWide,                                                                          pixelsHigh, 8,      // bits per component                                                                          bitmapBytesPerRow,                                                                          colorSpace,                                                                          kCGImageAlphaPremultipliedFirst); if (context == NULL)         {
                   free (bitmapData);                 fprintf (stderr, "Context not created!");         } // Make sure and release colorspace before returning         CGColorSpaceRelease( colorSpace ); return context; }