在平常開發(fā)中我們有時候會遇到要求我們獲取屏幕上某個點(diǎn)的顏色值胀蛮，或者對點(diǎn)擊的點(diǎn)上的顏色值進(jìn)行比較和判斷的院刁。接下來我們提供給大家兩種方法進(jìn)行操作與調(diào)用糯钙。

第一種

- (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]; }

第二種

- (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; }

在我項(xiàng)目中應(yīng)用到的實(shí)例中 我測試第一種測試顏色較準(zhǔn)粪狼，但是還沒有找到很好的解決完全正確的辦法退腥，如果各位游客有好的辦法，希望能夠留言給我再榄，謝謝