在平常开发中我们有时候会遇到要求我们获取屏幕上某个点的颜色值，或者对点击的点上的颜色值进行比较和判断的。接下来我们提供给大家两种方法进行操作与调用。
第一种
- (UIColor*)colorAtPixel:(CGPoint)point { // Cancel if point is outside image coordinates if (!CGRectContainsPoint(CGRectMake(0.0f, 0.0f, self.view.frame.size.width, self.view.frame.size.height), point)) { return nil; } NSInteger pointX = trunc(point.x); NSInteger pointY = trunc(point.y); CGImageRef cgImage = self.iconView.image.CGImage; NSUInteger width = self.view.frame.size.width; NSUInteger height = self.view.frame.size.height; CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); int bytesPerPixel = 4; int bytesPerRow = bytesPerPixel * 1; NSUInteger bitsPerComponent = 8; unsigned char pixelData[4] = { 0, 0, 0, 0 }; CGContextRef context = CGBitmapContextCreate(pixelData,1,1, bitsPerComponent, bytesPerRow, colorSpace, kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big); CGColorSpaceRelease(colorSpace); CGContextSetBlendMode(context, kCGBlendModeCopy); // Draw the pixel we are interested in onto the bitmap context CGContextTranslateCTM(context, -pointX, pointY - (CGFloat)height); CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, (CGFloat)width, (CGFloat)height), cgImage); CGContextRelease(context); // Convert color values [0..255] to floats [0.0..1.0] CGFloat red = (CGFloat)pixelData[0] / 255.0f; CGFloat green = (CGFloat)pixelData[1] / 255.0f; CGFloat blue = (CGFloat)pixelData[2] / 255.0f; CGFloat alpha = (CGFloat)pixelData[3] / 255.0f; NSLog(@" colors: RGB %f %f %f %f", red, green, blue, alpha); return [UIColor colorWithRed:red green:green blue:blue alpha:alpha]; }
第二种
- (UIColor*)getPixelColorAtLocation:(CGPoint)point { UIColor* color = nil; CGImageRef inImage = self.iconView.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; } 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. @try { int offset = 4 * ((w * round(point.y)) + round(point.x)); NSLog(@"offset: %d", offset); 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)]; } @catch (NSException* e) { NSLog(@"%@", [e reason]); } @finally { } } // 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 spacen"); return NULL; } // Allcate 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; }
在我项目中应用到的实例中 我测试第一种测试颜色较准，但是还没有找到很好的解决完全正确的办法，如果各位游客有好的办法，希望能够留言给我，谢谢
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