2

我目前正在使用这种技术来获取 UIimage 中像素的颜色。（在 iOS 上）

- (UIColor*) getPixelColorAtLocation:(CGPoint)point {
UIColor* color = nil;
CGImageRef inImage = self.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));
    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;

}

如此处所示；

http://www.markj.net/iphone-uiimage-pixel-color/

它工作得很好，但是当处理大于 UIImageView 的图像时它会失败。我尝试添加图像并更改缩放模式以适合视图。我将如何修改代码以使其仍然能够使用缩放图像对像素颜色进行采样。

4

3 回答 3

2

试试这个 swift3

func getPixelColor(image: UIImage, x: Int, y: Int, width: CGFloat) -> UIColor 
{

    let pixelData = CGDataProviderCopyData(CGImageGetDataProvider(image.CGImage))
    let data: UnsafePointer<UInt8> = CFDataGetBytePtr(pixelData)

    let pixelInfo: Int = ((Int(width) * y) + x) * 4

    let r = CGFloat(data[pixelInfo]) / CGFloat(255.0)
    let g = CGFloat(data[pixelInfo+1]) / CGFloat(255.0)
    let b = CGFloat(data[pixelInfo+2]) / CGFloat(255.0)
    let a = CGFloat(data[pixelInfo+3]) / CGFloat(255.0)

    return UIColor(red: r, green: g, blue: b, alpha: a)
}
于 2016-06-22T10:30:12.277 回答
0

这是一个指针：

0x3A28213A //sorry, I couldn't resist the joke

现在是真实的：在浏览了 markj.net 页面上的评论后，某位 James 建议进行以下更改：

size_t w = CGImageGetWidth(inImage); //Written by Mark
size_t h = CGImageGetHeight(inImage); //Written by Mark
float xscale = w / self.frame.size.width;
float yscale = h / self.frame.size.height;
point.x = point.x * xscale;
point.y = point.y * yscale;

（感谢http://www.markj.net/iphone-uiimage-pixel-color/comment-page-1/#comment-2159）

这实际上对我不起作用......并不是说我做了很多测试，而且我还不是世界上最伟大的程序员......

我的解决方案是以这样一种方式缩放UIImageView图像，使图像中的每个像素与屏幕上的标准 CGPoint 大小相同，然后我像正常一样（使用getPixelColorAtLocation:(CGPoint)point）取我的颜色，然后我将图像缩放回大小我想了。

希望这可以帮助！

于 2012-08-30T09:40:33.673 回答
-1

使用 UIImageView 层：

- (UIColor*) getPixelColorAtLocation:(CGPoint)point {
    UIColor* color = nil;

    UIGraphicsBeginImageContext(self.frame.size);
    CGContextRef cgctx = UIGraphicsGetCurrentContext();
    if (cgctx == NULL) { return nil; /* error */ }

    [self.layer renderInContext:cgctx];

    unsigned char* data = CGBitmapContextGetData (cgctx);
    /*
    ...
    */
    UIGraphicsEndImageContext();
    return color;
}
于 2012-08-30T10:07:11.413 回答