将 RGB 值传递给 CGContextSetRGBStrokeColor 无法正常工作

Question

对于橙色，我传递 rgb 值 255-140-0

CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);对我来说它画的是黄色！不是橙色的。

我尝试测试 CGContextSetRGBStokeColor 的一些低于 255 的随机值，它向我绘制白色。我不知道为什么会这样！

@ALL 任何人都可以在这个问题上给我建议吗

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{


    UITouch *touch = [touches anyObject];   
    CGPoint currentPoint = [touch locationInView:drawImage];
    currentPoint.y -= 20;
    UIGraphicsBeginImageContext(drawImage.frame.size);
    [drawImage.image drawInRect:CGRectMake(0, 0, drawImage.frame.size.width, drawImage.frame.size.height)];
    CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound);
    CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0);
    CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), red, green, blue, 1.0);

    CGContextBeginPath(UIGraphicsGetCurrentContext());
    CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y);
    CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), currentPoint.x, currentPoint.y);
    CGContextStrokePath(UIGraphicsGetCurrentContext());
    drawImage.image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
}

Answer 1

查看文档，它指出为 Red Green 和 Blue 传递的值是浮点数，

The graphics context for which to set the current stroke color.
red
The red intensity value for the color to set. The DeviceRGB color space permits the specification of a value ranging from 0.0 (zero intensity) to 1.0 (full intensity).
green
The green intensity value for the color to set. The DeviceRGB color space permits the specification of a value ranging from 0.0 (zero intensity) to 1.0 (full intensity).
blue
The blue intensity value for the color to set. The DeviceRGB color space permits the specification of a value ranging from 0.0 (zero intensity) to 1.0 (full intensity).
alpha
A value that specifies the opacity level. Values can range from 0.0 (transparent) to 1.0 (opaque). Values outside this range are clipped to 0.0 or 1.0.

因此这些值必须在 0.0 和 1.0 之间。您输入的数字太大。以后，请先检查文档。