iphone - Obtener el color de píxel de UIImage

rgb pixel

Question

¿Cómo puedo obtener el valor RGB de un píxel en particular en un UIImage?

Answer 1

Algunos códigos Swift basados ​​en la respuesta de Minas. He extendido UIImage para que sea accesible en todas partes, y he agregado una lógica simple para adivinar el formato de imagen basado en el paso de píxeles (1, 3 o 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()
}
}
}

Actualizado para 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 2

Aquí hay un método genérico para obtener el color del píxel en una imagen UI, basándose en la respuesta 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];
}

Tenga en cuenta que X e Y pueden intercambiarse; esta función accede directamente al mapa de bits subyacente y no considera las rotaciones que pueden ser parte del UIImage.

Answer 3

En primer lugar, cree y adjunte un reconocedor de gestos de toque que permita las interacciones del usuario:

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

Ahora implementa -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();
}

Esto funcionará en UILabel con fondo transparente, si esto no es lo que quieres puedes comparar alfa, rojo, verde, azul con self.label.backgroundColor ...

Answer 4

No puede acceder directamente a los datos brutos, pero al obtener la CGImage de esta imagen puede acceder a ella. aquí hay un enlace a otra pregunta que responde a su pregunta y otras que podría tener con respecto a la manipulación detallada de la imagen: CGImage

Answer 5

Prueba este código muy simple:

Solía ​​detectar una pared en mi juego de laberinto (la única información que necesito es el canal alfa, pero incluí el código para obtener los otros colores para ti):

- (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 6

En contacto

-(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 7

- (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];
}