目标-c:如何旋转CGRect [英] Objective-c: How to rotate CGRect
问题描述
我尝试旋转矩形,但是无法正常工作.
I've tried to rotate my rectangle, but it does not work properly.
这是我的代码的一部分,我在另一篇文章中找到了它:
Here is part of my code, I found it in another post:
#define DEGREES_TO_RADIANS(x) (M_PI * x / 180.0)
-(void)drawRect:(NSRect)rect
{
CGContextRef cRef = [[NSGraphicsContext currentContext] graphicsPort];
// points[] - this is a CGPoints array, length_one is a double value
CGRect rect_one = CGRectMake(points[0].x, points[0].y, (CGFloat)length_one, 40);
// I've print out the origin of old one and new one
NSLog(@"old rect -- %f, %f", rect_one.origin.x, rect_one.origin.y);
float centerX = rect_one.origin.x + (rect_one.size.width / 2.0);
float centerY = rect_one.origin.y + (rect_one.size.height / 2.0);
CGAffineTransform rotation = CGAffineTransformMakeRotation(DEGREES_TO_RADIANS(10));
CGAffineTransform moveAnchor = CGAffineTransformMakeTranslation(centerX, centerY);
CGAffineTransform centeredRotation = CGAffineTransformConcat(moveAnchor, rotation);
CGRect rotatedRect = CGRectApplyAffineTransform(rect_one, centeredRotation);
CGContextAddRect(cRef, rotatedRect);
// new one
NSLog(@"new rect -- %f, %f", rotatedRect.origin.x, rotatedRect.origin.y);
}
即使我从视图中找不到新的矩形,原点也发生了很大变化. 旧的原点是(x = 263.3,y = 502.8),新的原点是(x = 506.1,y = 1132.0)这个系统如何工作,尤其是如何分配旋转角度?如果可能的话,你们能帮我简要解释一下吗.非常感谢!!!
And the origin changed a lot even I can not find my new rectangle from the view. Old origin is (x = 263.3, y = 502.8) and the new origin is (x=506.1, y=1132.0) How does this system work especially how to assign the angle of rotation? If possible, could you guys help me brief explain it. Thanks a lot!!!!
推荐答案
正如其他人所说,NSRect
或CGRect
始终是与轴对齐的矩形. CGRectApplyAffineTransform
返回转换后的矩形的与轴对齐的边界框:
As others have said, an NSRect
or CGRect
is always an axis-aligned rectangle. CGRectApplyAffineTransform
returns the axis-aligned bounding box of the translated rectangle:
请注意,如果应用旋转,则新矩形(边界框)的尺寸可能会与原始矩形不同.这意味着如果要绘制转换后的矩形,则对矩形应用转换是没有用的.
Note that the new rectangle (the bounding box) is likely to have different dimensions than the original rectangle, if you applied a rotation. This means it's useless to apply a transform to a rectangle if you want to draw the transformed rectangle.
相反,您需要变换图形上下文的坐标系.这样想:您正在桌上的一张纸上画画.您总是绘制一个与桌子边缘对齐的矩形.要绘制旋转的矩形,请旋转纸张,然后照常绘制一个矩形.更改CTM就像旋转(或移动,缩小或扩展)纸张.
Instead, you need to transform the coordinate system of the graphics context. Think of it like this: you're drawing on a sheet of paper on a desk. You always draw a rectangle that is aligned to the edges of the desk. To draw a rotated rectangle, you rotate the paper, then draw a rectangle as usual. Changing the CTM is like rotating (or moving or shrinking or expanding) the sheet of paper.
-(void)drawRect:(NSRect)rect {
CGContextRef gc = [[NSGraphicsContext currentContext] graphicsPort];
// points[] - this is a CGPoints array, length_one is a double value
CGRect rect = CGRectMake(points[0].x, points[0].y, (CGFloat)length_one, 40);
CGFloat xMid = CGRectGetMidX(rect);
CGFloat yMid = CGRectGetMidY(rect);
CGContextSaveGState(gc); {
// Translate the origin to the midpoint of the rectangle, because rotations
// always happen around the origin.
CGContextTranslateCTM(gc, xMid, yMid);
// Rotate the coordinate system by 10 degrees.
CGContextRotateCTM(gc, 10 * M_PI / 180);
// Prepare a new rectangle, with the same size as the original rectangle
// but centered on the origin.
CGRect newRect = rect;
newRect.origin.x = -newRect.size.width / 2;
newRect.origin.y = -newRect.size.height / 2;
// Add the rectangle to the context's path.
CGContextAddRect(gc, newRect);
// Draw the new rectangle.
CGContextSetFillColorWithColor(gc, [NSColor lightGrayColor].CGColor);
CGContextSetStrokeColorWithColor(gc, [NSColor blackColor].CGColor);
CGContextSetLineWidth(gc, 2);
CGContextSetLineJoin(gc, kCGLineJoinMiter);
CGContextDrawPath(gc, kCGPathFillStroke);
} CGContextRestoreGState(gc);
}
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