Obtenir la couleur de pixel de UIImage

Question

Comment puis-je obtenir la valeur RVB d'un pixel particulier dans un UIImage?

Answer 1

Vous ne pouvez pas accéder directement aux données brutes, mais en obtenant la CGImage de cette image, vous pouvez y accéder. Voici un lien vers une autre question qui répond à votre question et à d’autres que vous pourriez avoir concernant la manipulation d’images détaillées: CGImage

Answer 2

Essayez ce code très simple:

Je détectais un mur dans mon jeu de labyrinthe (la seule information dont j'ai besoin est le canal alpha, mais j'ai inclus le code pour obtenir les autres couleurs):

- (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

Voici une méthode générique pour obtenir une couleur de pixel dans une image d'interface utilisateur, en s'appuyant sur la réponse de Minas Petterson:

- (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];
}

Notez que X et Y peuvent être échangés; cette fonction accède directement au bitmap sous-jacent et ne prend pas en compte les rotations pouvant faire partie de UIImage.

Answer 5

- (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 6

Un code Swift basé sur la réponse de Minas. J'ai étendu UIImage pour le rendre accessible partout, et j'ai ajouté une logique simple pour deviner le format d'image basé sur la foulée en pixels (1, 3 ou 4)

Swift 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()
    }
  }
} 

Mise à jour pour Swift 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
    }
}

Answer 7

Tout d’abord, créez et attachez un identificateur de gestes tactiles pour autoriser les interactions entre utilisateurs:

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

Maintenant, implémentez -tapGesture:

- (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();
}

Cela fonctionnera sur UILabel avec un arrière-plan transparent. Si ce n’est pas ce que vous voulez, vous pouvez comparer alpha, rouge, vert, bleu avec self.label.backgroundColor...