我正在使用代码渲染圆形渐变并通过触摸在渐变上创建十字准线(子视图)。我现在想读取触摸位置的像素,并使其返回RGB值,但是它始终为我提供相同的值。
编辑:添加了呈现渐变的代码
完整的新代码:
viewDidLoad
- (void)viewDidLoad
{
[super viewDidLoad];
CGSize size = CGSizeMake(self.view.bounds.size.width, self.view.bounds.size.height);
UIGraphicsBeginImageContextWithOptions(CGSizeMake(size.width, size.height), YES, 0.0);
[[UIColor whiteColor] setFill];
UIRectFill(CGRectMake(0, 0, size.width, size.height));
int sectors = 180;
float radius = MIN((size.width - 100), (size.height - 100))/2;
float angle = 2 * M_PI/sectors;
UIBezierPath *bezierPath;
for ( int i = 0; i < sectors; i++)
{
CGPoint center = CGPointMake((size.width/2), (size.height/2));
bezierPath = [UIBezierPath bezierPathWithArcCenter:center radius:radius startAngle:i * angle endAngle:(i + 1) * angle clockwise:YES];
[bezierPath addLineToPoint:center];
[bezierPath closePath];
UIColor *color = [UIColor colorWithHue:((float)i)/sectors saturation:1. brightness:1. alpha:1];
[color setFill];
[color setStroke];
[bezierPath fill];
[bezierPath stroke];
}
img = UIGraphicsGetImageFromCurrentImageContext();
iv = [[UIImageView alloc] initWithImage:img];
[self.view addSubview:iv];
[self.view addSubview:ch];
}
我的平移手势识别器:
- (IBAction)handlePan:(UIPanGestureRecognizer *)sender {
CGPoint translation = [sender translationInView:self.view];
[sender setTranslation:CGPointZero inView:self.view];
CGPoint center = sender.view.center;
center.x += translation.x;
center.y += translation.y;
sender.view.center = center;
CGPoint colorPoint = [sender.view.superview convertPoint:center toView:iv];
[sender setTranslation:CGPointMake(0, 0) inView:self.view];
CFDataRef pixelData = CGDataProviderCopyData(CGImageGetDataProvider(img.CGImage));
const UInt8* data = CFDataGetBytePtr(pixelData);
int pixelInfo = (img.size.width * colorPoint.y ) +colorPoint.x ;
float red = data[pixelInfo];
float green = data[(pixelInfo + 1)];
float blue = data[pixelInfo + 2];
float alpha = data[pixelInfo + 3];
UIColor *pixelcolor = [UIColor colorWithRed:red/255 green:green/255 blue:blue/255 alpha:alpha]; // The pixel color info
CFRelease(pixelData);
NSLog(@"Color Value : %f, %f, %f, %f",red,green,blue,alpha);
}
一些NSLogs:
2013-07-05 10:04:20.913 ColorPicker[614:11603] pixel color: 156, 212, 255
2013-07-05 10:04:20.929 ColorPicker[614:11603] pixel color: 156, 212, 255
2013-07-05 10:04:20.947 ColorPicker[614:11603] pixel color: 156, 212, 255
2013-07-05 10:04:21.014 ColorPicker[614:11603] pixel color: 156, 212, 255
2013-07-05 10:04:21.047 ColorPicker[614:11603] pixel color: 156, 212, 255
2013-07-05 10:04:21.447 ColorPicker[614:11603] pixel color: 156, 212, 255
编辑:颜色也不正确。我在一开始就得到了不同的RGB值,然后该值改变一次并保持不变。
glReadPixels这么慢,还是我的帧缓冲区出了问题?
最佳答案
您将在每个检测到的事件后重置手势识别器的转换。这意味着colorPoint
中的坐标变化不大。
您应该通过使用colorPoint
并将其转换为sender.view.center
的坐标系来计算iv
。
CGPoint translation = [sender translationInView:self.view];
[sender setTranslation:CGPointZero inView:self.view];
CGPoint center = sender.view.center;
center.x += translation.x;
center.y += translation.y;
sender.view.center = center;
CGPoint colorPoint = [sender.view.superview convertPoint:center toView:iv];
现在
colorPoint
是手势识别器视图的当前位置,以iv
的坐标系表示。