Question

我在iPad上有一个png图像，尺寸为1214x1214（并且是视网膜的两倍），并将其设置为位于屏幕坐标（0，-20）的UIImageView。为了在设备旋转/方向更改期间它适合屏幕，我将其设置为Aspect Fit类型。

我想要做的是能够触摸屏幕并读取触摸下方像素的RGB值。我已经实现了一个UIGestureRecognizer并将其绑定到UIImage并成功恢复了坐标。

给我带来麻烦的是我尝试了几种检索RGB值的方法（例如[如何获取iphone上图像上像素的RGB值]）1 但我的RGB值看起来好像图像偏斜并映射到UIView上的不同位置。

我的问题是，我怎样才能满足这样的事实：我将UIImageView设置为Aspect Fit，以及设备可能是横向或纵向（颠倒或向上）的事实？

Answer 1

好的，所以我把它解决了，这可能对那些试图做类似事情的人有所帮助。

我使用此函数从另一个答案计算了图像的缩放大小

-(CGRect)frameForImage:(UIImage*)image inImageViewAspectFit:(UIImageView*)imageView
{
    float imageRatio = image.size.width / image.size.height;

    float viewRatio = imageView.frame.size.width / imageView.frame.size.height;

    if(imageRatio < viewRatio)
    {
        float scale = imageView.frame.size.height / image.size.height;

        float width = scale * image.size.width;

        float topLeftX = (imageView.frame.size.width - width) * 0.5;

        return CGRectMake(topLeftX, 0, width, imageView.frame.size.height);
    }
    else
    {
        float scale = imageView.frame.size.width / image.size.width;

        float height = scale * image.size.height;

        float topLeftY = (imageView.frame.size.height - height) * 0.5;

        return CGRectMake(0, topLeftY, imageView.frame.size.width, height);
    }
}

将注册函数作为监听器

取得了接触点

CGPoint tapPoint = [sender locationInView:imageMap];

根据我的图像移动位置改变了触摸点

if([UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationPortrait ||
   [UIApplication sharedApplication].statusBarOrientation == UIInterfaceOrientationPortraitUpsideDown )
  {
  // portrait (y has increased, x has stayed the same)
  tapPoint.y -= rectScaleSize.origin.y;
  }
else  
  {
  // landscape (x has increased, y has stayed the same)
  tapPoint.x -= rectScaleSize.origin.x;
  }

然后根据图像的原始大小及其纵横比适合大小重新调整

tapPoint.x = (tapPoint.x * imageMap.image.size.width) / rectScaleSize.size.width;
tapPoint.y = (tapPoint.y * imageMap.image.size.height) / rectScaleSize.size.height;

其中imageMap.image是我的原始图像，而rectScaleSize是从frameForImage函数返回的

，最后得到RGB值

CGImageRef image  = [imageMap.image CGImage];
NSUInteger width  = CGImageGetWidth(image);
NSUInteger height = CGImageGetHeight(image);
// NSLog(@"RGB Image is %d x %d",width,height);

CGColorSpaceRef colorSpace  = CGColorSpaceCreateDeviceRGB();
unsigned char *rawData      = malloc(height * width * 4);
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),image);
CGContextRelease(context);

int byteIndex = (bytesPerRow * (int)tapPoint.y) + (int)tapPoint.x * bytesPerPixel;
int red = rawData[byteIndex];
int green = rawData[byteIndex + 1];
int blue = rawData[byteIndex + 2];
//int alpha = rawData[byteIndex + 3];

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

似乎工作得很好，希望它有用。如果我做了一些非常错误的话，欢迎评论！

缩放后在UIImageView内的位置查找RGB值

1 个答案: