獲取UIImage的像素顏色

Question

如何獲取UIImage中特定像素的RGB值？

Answer 1

您不能直接訪問原始數據，但通過獲取此圖像的CGImage，您可以訪問它。這裏是，回答你的問題，其他人則可能有關於詳細的圖像處理另一個問題的鏈接：CGImage

Answer 2

試試這個非常簡單的代碼：

我用來檢測我的迷宮遊戲牆（唯一的信息我需要的是alpha通道，但是我包括代碼來獲取等多種顏色供你）：

- (BOOL)isWallPixel:(UIImage *)image xCoordinate:(int)x yCoordinate:(int)y { 

    CFDataRef pixelData = CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage)); 
    const UInt8* data = CFDataGetBytePtr(pixelData); 

    int pixelInfo = ((image.size.width * y) + x) * 4; // The image is png 

    //UInt8 red = data[pixelInfo];   // If you need this info, enable it 
    //UInt8 green = data[(pixelInfo + 1)]; // If you need this info, enable it 
    //UInt8 blue = data[pixelInfo + 2]; // If you need this info, enable it 
    UInt8 alpha = data[pixelInfo + 3];  // I need only this info for my maze game 
    CFRelease(pixelData); 

    //UIColor* color = [UIColor colorWithRed:red/255.0f green:green/255.0f blue:blue/255.0f alpha:alpha/255.0f]; // The pixel color info 

    if (alpha) return YES; 
    else return NO; 

} 

Answer 3

OnTouch

-(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event 
{ 
    UITouch *touch = [[touches allObjects] objectAtIndex:0]; 
    CGPoint point1 = [touch locationInView:self.view]; 
    touch = [[event allTouches] anyObject]; 
    if ([touch view] == imgZoneWheel) 
    { 
     CGPoint location = [touch locationInView:imgZoneWheel]; 
     [self getPixelColorAtLocation:location]; 
     if(alpha==255) 
     { 
      NSLog(@"In Image Touch view alpha %d",alpha); 
      [self translateCurrentTouchPoint:point1.x :point1.y]; 
      [imgZoneWheel setImage:[UIImage imageNamed:[NSString stringWithFormat:@"blue%d.png",GrndFild]]]; 
     } 
    } 
} 



- (UIColor*) getPixelColorAtLocation:(CGPoint)point 
{ 

    UIColor* color = nil; 

    CGImageRef inImage; 

    inImage = imgZoneWheel.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)); 
     alpha = data[offset]; 
     int red = data[offset+1]; 
     int green = data[offset+2]; 
     int blue = data[offset+3]; 
     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; 
} 

Answer 4

所有創建和附加輕敲手勢識別的

首先，請允許允許用戶交互：

UITapGestureRecognizer * tapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapGesture:)]; 
[self.label addGestureRecognizer:tapRecognizer]; 
self.label.userInteractionEnabled = YES; 

現在實行​​

- (void)tapGesture:(UITapGestureRecognizer *)recognizer 
{ 
    CGPoint point = [recognizer locationInView:self.label]; 

    UIGraphicsBeginImageContext(self.label.bounds.size); 
    CGContextRef context = UIGraphicsGetCurrentContext(); 
    [self.label.layer renderInContext:context]; 

    int bpr = CGBitmapContextGetBytesPerRow(context); 
    unsigned char * data = CGBitmapContextGetData(context); 
    if (data != NULL) 
    { 
     int offset = bpr*round(point.y) + 4*round(point.x); 
     int blue = data[offset+0]; 
     int green = data[offset+1]; 
     int red = data[offset+2]; 
     int alpha = data[offset+3]; 

     NSLog(@"%d %d %d %d", alpha, red, green, blue); 

     if (alpha == 0) 
     { 
      // Here is tap out of text 
     } 
     else 
     { 
      // Here is tap right into text 
     } 
    } 

    UIGraphicsEndImageContext(); 
} 

這將適用於的UILabel與透明的背景下，如果這不是你想要的你可以比較阿爾法，紅色，綠色，藍色與self.label.backgroundColor ...

Answer 5

這是一個通用的方法獲取像素顏色的UI圖像，基於米納斯佩特森'回答：

- (UIColor*)pixelColorInImage:(UIImage*)image atX:(int)x atY:(int)y { 

    CFDataRef pixelData = CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage)); 
    const UInt8* data = CFDataGetBytePtr(pixelData); 

    int pixelInfo = ((image.size.width * y) + x) * 4; // 4 bytes per pixel 

    UInt8 red = data[pixelInfo + 0]; 
    UInt8 green = data[pixelInfo + 1]; 
    UInt8 blue = data[pixelInfo + 2]; 
    UInt8 alpha = data[pixelInfo + 3]; 
    CFRelease(pixelData); 

    return [UIColor colorWithRed:red /255.0f 
          green:green/255.0f 
          blue:blue /255.0f 
          alpha:alpha/255.0f]; 
} 

請注意，X和Y可以交換;此函數直接訪問底層位圖，並不考慮可能是UIImage的一部分的旋轉。

Answer 6

- (UIColor *)colorAtPixel:(CGPoint)point inImage:(UIImage *)image { 

    if (!CGRectContainsPoint(CGRectMake(0.0f, 0.0f, image.size.width, image.size.height), point)) { 
     return nil; 
    } 

    // Create a 1x1 pixel byte array and bitmap context to draw the pixel into. 
    NSInteger pointX = trunc(point.x); 
    NSInteger pointY = trunc(point.y); 
    CGImageRef cgImage = image.CGImage; 
    NSUInteger width = image.size.width; 
    NSUInteger height = image.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; 
    return [UIColor colorWithRed:red green:green blue:blue alpha:alpha]; 
} 

Answer 7

一些基於Minas答案的Swift代碼。我已經擴展的UIImage使其到處訪問，並且我已經增加了一些簡單的邏輯來猜測基於所述像素跨度的圖像格式（1，3，或4）

夫特3：

public extension UIImage { 
    func getPixelColor(point: CGPoint) -> UIColor { 
    guard let pixelData = CGDataProviderCopyData(CGImageGetDataProvider(self.CGImage)) else { 
     return UIColor.clearColor() 
    } 
    let data = CFDataGetBytePtr(pixelData) 
    let x = Int(point.x) 
    let y = Int(point.y) 
    let index = Int(self.size.width) * y + x 
    let expectedLengthA = Int(self.size.width * self.size.height) 
    let expectedLengthRGB = 3 * expectedLengthA 
    let expectedLengthRGBA = 4 * expectedLengthA 
    let numBytes = CFDataGetLength(pixelData) 
    switch numBytes { 
    case expectedLengthA: 
     return UIColor(red: 0, green: 0, blue: 0, alpha: CGFloat(data[index])/255.0) 
    case expectedLengthRGB: 
     return UIColor(red: CGFloat(data[3*index])/255.0, green: CGFloat(data[3*index+1])/255.0, blue: CGFloat(data[3*index+2])/255.0, alpha: 1.0) 
    case expectedLengthRGBA: 
     return UIColor(red: CGFloat(data[4*index])/255.0, green: CGFloat(data[4*index+1])/255.0, blue: CGFloat(data[4*index+2])/255.0, alpha: CGFloat(data[4*index+3])/255.0) 
    default: 
     // unsupported format 
     return UIColor.clearColor() 
    } 
    } 
} 

更新了雨燕4：

func getPixelColor(_ image:UIImage, _ point: CGPoint) -> UIColor { 
    let cgImage : CGImage = image.cgImage! 
    guard let pixelData = CGDataProvider(data: (cgImage.dataProvider?.data)!)?.data else { 
     return UIColor.clear 
    } 
    let data = CFDataGetBytePtr(pixelData)! 
    let x = Int(point.x) 
    let y = Int(point.y) 
    let index = Int(image.size.width) * y + x 
    let expectedLengthA = Int(image.size.width * image.size.height) 
    let expectedLengthRGB = 3 * expectedLengthA 
    let expectedLengthRGBA = 4 * expectedLengthA 
    let numBytes = CFDataGetLength(pixelData) 
    switch numBytes { 
    case expectedLengthA: 
     return UIColor(red: 0, green: 0, blue: 0, alpha: CGFloat(data[index])/255.0) 
    case expectedLengthRGB: 
     return UIColor(red: CGFloat(data[3*index])/255.0, green: CGFloat(data[3*index+1])/255.0, blue: CGFloat(data[3*index+2])/255.0, alpha: 1.0) 
    case expectedLengthRGBA: 
     return UIColor(red: CGFloat(data[4*index])/255.0, green: CGFloat(data[4*index+1])/255.0, blue: CGFloat(data[4*index+2])/255.0, alpha: CGFloat(data[4*index+3])/255.0) 
    default: 
     // unsupported format 
     return UIColor.clear 
    } 
}