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ioscore-graphicscgcontext

When drawing an arc using CGContextAddArcToPoint(), what does (x1,y1) and (x2,y2) mean?

You can use the following code to draw an arc using Quartz:

CGContextMoveToPoint(context2, x, y);
CGContextAddArcToPoint(context2, x1, y1, x2, y2, r);

In these functions, (x,y) is the starting point and r is the arc radius but what are (x1,y1) and (x2,y2)?

Solution

  • http://developer.apple.com/library/ios/documentation/GraphicsImaging/Reference/CGContext/Reference/reference.html#//apple_ref/c/func/CGContextAddArcToPoint

    x1: The x-value, in user space coordinates, for the end point of the first tangent line. The first tangent line is drawn from the current point to (x1,y1).

    y1: The y-value, in user space coordinates, for the end point of the first tangent line. The first tangent line is drawn from the current point to (x1,y1).

    x2: The x-value, in user space coordinates, for the end point of the second tangent line. The second tangent line is drawn from (x1,y1) to (x2,y2).

    y2: The y-value, in user space coordinates, for the end point of the second tangent line. The second tangent line is drawn from (x1,y1) to (x2,y2).