我知道这是一个常见的问题，这个问题有很多答案。我已经使用了其中一些。虽然其中很多都是一样的。但令我伤心的是，他们都没有为我工作。以下我用过的代码。
-(void)getRGBAsFromImage:(UIImage*)image atX:(int)xx andY:(int)yy
{
// First get the image into your data buffer
CGImageRef imageRef = [image CGImage];
NSUInteger width = CGImageGetWidth(imageRef);
NSUInteger height = CGImageGetHeight(imageRef);
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData = (unsigned char*) calloc(height * width * 4, sizeof(unsigned char));
NSUInteger bytesPerPixel = 4;
NSUInteger bytesPerRow = bytesPerPixel * width;
NSUInteger bitsPerComponent = 8;
CGContextRef context = CGBitmapContextCreate(rawData, width, height,
bitsPerComponent, bytesPerRow, colorSpace,
kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big);
CGColorSpaceRelease(colorSpace);
CGContextDrawImage(context, CGRectMake(0, 0, width, height), imageRef);
CGContextRelease(context);
// Now your rawData contains the image data in the RGBA8888 pixel format.
int byteIndex = (bytesPerRow * yy) + xx * bytesPerPixel;
CGFloat red = (rawData[byteIndex] * 1.0) / 255.0;
CGFloat green = (rawData[byteIndex + 1] * 1.0) / 255.0;
CGFloat blue = (rawData[byteIndex + 2] * 1.0) / 255.0;
CGFloat alpha = (rawData[byteIndex + 3] * 1.0) / 255.0;
byteIndex += 4;
NSLog(@"the vale of the rbg of red is %f",red);
demoColor.tintColor = [UIColor colorWithRed:red green:green blue:blue alpha:alpha];
free(rawData);
}
这是我用过的另一种方法 -
- (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 = CGColorSpaceCreateWithName(kCGColorSpaceGenericRGB);
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;
}
- (UIColor*) getPixelColorAtLocation:(CGPoint)point {
UIColor* color = nil;
//CGImageRef inImage = self.image.CGImage;
CGImageRef inImage = [AppDelegate getInstance].capturedImage.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));
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)];
}
// When finished, release the context
CGContextRelease(cgctx);
// Free image data memory for the context
if (data) { free(data); }
return color;
}
但这些都不适用于我。请帮我解决这个问题。有什么我想念的吗？
我的UI中有2个UIImageView。后面的那个包含我需要选择被触摸的像素颜色的图像。另一个UIImageView是用拾取的颜色在背面图像上绘画。
请帮忙。任何帮助将非常感谢。
答案 0 :(得分：49)
这是我使用过的，它看起来比你尝试过的方法简单。
在我的自定义视图类中，我有：
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
UITouch *touch = [[event allTouches] anyObject];
CGPoint loc = [touch locationInView:self];
self.pickedColor = [self colorOfPoint:loc];
}
colorOfPoint是UIView上类别中的方法，代码如下：
#import "UIView+ColorOfPoint.h"
#import <QuartzCore/QuartzCore.h>
@implementation UIView (ColorOfPoint)
-(UIColor *) colorOfPoint:(CGPoint)point
{
unsigned char pixel[4] = {0};
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef context = CGBitmapContextCreate(pixel,
1, 1, 8, 4, colorSpace, (CGBitmapInfo)kCGImageAlphaPremultipliedLast);
CGContextTranslateCTM(context, -point.x, -point.y);
[self.layer renderInContext:context];
CGContextRelease(context);
CGColorSpaceRelease(colorSpace);
UIColor *color = [UIColor colorWithRed:pixel[0]/255.0
green:pixel[1]/255.0 blue:pixel[2]/255.0
alpha:pixel[3]/255.0];
return color;
}
不要忘记将类别导入自定义视图类并添加QuartzCore框架。
2013年的简单说明：将最后一个参数强制转换为（CGBitmapInfo）以避免隐式转换警告：示例here。希望它有所帮助。
答案 1 :(得分：12)
感谢@ Aggressor发布上面的代码
Swift 2.1
func getPixelColorAtPoint(point:CGPoint) -> UIColor{
let pixel = UnsafeMutablePointer<CUnsignedChar>.alloc(4)
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedLast.rawValue)
let context = CGBitmapContextCreate(pixel, 1, 1, 8, 4, colorSpace, bitmapInfo.rawValue)
CGContextTranslateCTM(context, -point.x, -point.y)
view.layer.renderInContext(context!)
let color:UIColor = UIColor(red: CGFloat(pixel[0])/255.0, green: CGFloat(pixel[1])/255.0, blue: CGFloat(pixel[2])/255.0, alpha: CGFloat(pixel[3])/255.0)
pixel.dealloc(4)
return color
}
Swift 3 ，Xcode版本8.2（8C38）和 Swift 4 ，Xcode版本9.1（9B55）
func getPixelColorAtPoint(point:CGPoint, sourceView: UIView) -> UIColor{
let pixel = UnsafeMutablePointer<CUnsignedChar>.allocate(capacity: 4)
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
let context = CGContext(data: pixel, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)
var color: UIColor? = nil
if let context = context {
context.translateBy(x: -point.x, y: -point.y)
sourceView.layer.render(in: context)
color = UIColor(red: CGFloat(pixel[0])/255.0,
green: CGFloat(pixel[1])/255.0,
blue: CGFloat(pixel[2])/255.0,
alpha: CGFloat(pixel[3])/255.0)
pixel.deallocate(capacity: 4)
}
return color
}
答案 2 :(得分：9)
很棒的答案rdelmar这对我很有帮助！
以下是我在Swift中完成上述操作的方法：
override func touchesBegan(touches: NSSet, withEvent event: UIEvent)
{
var touch:UITouch = event.allTouches()!.anyObject() as UITouch
var loc = touch.locationInView(self)
var color:UIColor = getPixelColorAtPoint(loc)
println(color)
}
//returns the color data of the pixel at the currently selected point
func getPixelColorAtPoint(point:CGPoint)->UIColor
{
let pixel = UnsafeMutablePointer<CUnsignedChar>.alloc(4)
var colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue)
let context = CGBitmapContextCreate(pixel, 1, 1, 8, 4, colorSpace, bitmapInfo)
CGContextTranslateCTM(context, -point.x, -point.y)
layer.renderInContext(context)
var color:UIColor = UIColor(red: CGFloat(pixel[0])/255.0, green: CGFloat(pixel[1])/255.0, blue: CGFloat(pixel[2])/255.0, alpha: CGFloat(pixel[3])/255.0)
pixel.dealloc(4)
return color
}
答案 3 :(得分：9)
这是上述所有答案的组合，但在扩展名
中extension UIImageView {
func getPixelColorAt(point:CGPoint) -> UIColor{
let pixel = UnsafeMutablePointer<CUnsignedChar>.allocate(capacity: 4)
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
let context = CGContext(data: pixel, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)
context!.translateBy(x: -point.x, y: -point.y)
layer.render(in: context!)
let color:UIColor = UIColor(red: CGFloat(pixel[0])/255.0,
green: CGFloat(pixel[1])/255.0,
blue: CGFloat(pixel[2])/255.0,
alpha: CGFloat(pixel[3])/255.0)
pixel.deallocate(capacity: 4)
return color
}
}
override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
let touch = touches.first
if let point = touch?.location(in: view) {
let color = myUIImageView.getPixelColorAt(point: point)
print(color)
}
}
答案 4 :(得分：0)
首先，我想感谢这段代码的作者，它为我的游戏项目提供了很多帮助，因为我一直在寻找该功能来做一个像素完美的击打盒（不包括aplha是O的地方）。这是Swift 5的一些更新：
// Fonction permettant de retourner les valeurs RGBA d'un pixel d'une vue
func getPixelColor(atPosition:CGPoint) -> UIColor{
var pixel:[CUnsignedChar] = [0, 0, 0, 0];
let colorSpace = CGColorSpaceCreateDeviceRGB();
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue);
let context = CGContext(data: &pixel, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: colorSpace, bitmapInfo: bitmapInfo.rawValue);
context!.translateBy(x: -atPosition.x, y: -atPosition.y);
layer.render(in: context!);
let color:UIColor = UIColor(red: CGFloat(pixel[0])/255.0,
green: CGFloat(pixel[1])/255.0,
blue: CGFloat(pixel[2])/255.0,
alpha: CGFloat(pixel[3])/255.0);
return color;
}
我在pixel.dealloc（4）方面遇到了严重问题，因为在Swift 5中似乎无法再通过容量参数进行释放。我删除了（4），但是它有一些奇怪的行为（因为dealloc（）并没有释放整个数组）。
我没有对UIView进行扩展，因为在我的项目中我有自己的子类，但这很容易做到。
我实现代码的方式：
// Méthode déterminant si le "touch" est validé par l'objet (par défaut, exclut les zones transparentes et les objets invisibles). A surcharger si nécessaire.
func isHit(atPosition position:CGPoint) -> Bool
{
// Si l'objet n'est pas caché (paramètre isHidden) et si la zone touchée correspond à une zone effectivement dessinée (non transparente), retourne true.
if (!self.isHidden && self.getPixelColor(atPosition: position).cgColor.alpha != 0) {return true}
else {return false}
}
我希望这会有所帮助。