//下面代码放在UIImageVIew类的.m下，实现第一个方法即可。
//传入一个坐标点，返回相应的颜色
- (UIColor*) getPixelColorAtLocation:(CGPoint)point {
UIColor* color =nil;
CGImageRefinImage =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
CGContextRefcgctx = [selfcreateARGBBitmapContextFromImage:inImage];
if(cgctx ==NULL) {
returnnil;/* error */
}
size_tw =CGImageGetWidth(inImage);
size_th =CGImageGetHeight(inImage);
CGRectrect = {{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.
unsignedchar* 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.
intoffset =4*((w*round(point.y))+round(point.x));
intalpha =data[offset];
intred = data[offset+1];
intgreen = data[offset+2];
intblue = data[offset+3];
//NSLog(@"offset: %i colors: RGB A %i %i %i%i",offset,red,green,blue,alpha);
color = [UIColorcolorWithRed:(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); }
returncolor;
}
- (CGContextRef) createARGBBitmapContextFromImage:(CGImageRef) inImage {
CGContextRefcontext =NULL;
CGColorSpaceRefcolorSpace;
void*bitmapData;
intbitmapByteCount;
intbitmapBytesPerRow;
// Get image width, height. We'll use the entire image.
size_tpixelsWide =CGImageGetWidth(inImage);
size_tpixelsHigh =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");
returnNULL;
}
// 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 );
returnNULL;
}
// 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 );
returncontext;
}