How do I draw a point using Core Graphics?

问题:

I see APIs in Quartz for drawing lines and circles. But all I want to do is to specify the (x,y) cartesian coordinate to color a pixel a particular value. How do I do that?

回答1:

CGContextFillRect(context, CGRectMake(x,y,1,1));

回答2:

Quartz is not a pixel-oriented API, and its contexts aren’t necessarily pixel buffers. If you want to draw pixmaps, create a bitmap context with CGBitmapContextCreate(). You provide a buffer, which you can manipulate directly, and can copy to another context by creating a CGImage from the same buffer using CGImageCreate() and drawing that.

回答3:

I got a point (zero length line) to draw after setting the line-caps to kCGLineCapRound. The default line-cap has no length so can't be drawn.

The argument that a point has no size is silly. The lines have no width but we can draw those (by using the "line width" from the draw state). A point should draw in exactly the same way, and with different line caps I believe it does.

Maybe this behavior is new?

回答4:

Draw a very small ellipse/circle and fill it!

CGContextAddEllipseInRect(Context,(CGRectMake (x_dot, y_dot, 3.0, 3.0));
CGContextDrawPath(Context, kCGPathFill);
CGContextStrokePath(Context);

I am using this code to create a small dot (3x3 pixels) in a dotted music note.

回答5:

You can draw a 1-pixel-length line at the coordinate in question; that should accomplish what you want.

回答6:

I'm having the same issue - i find the best solution is similar to the last, but at least it doesn't leave something that looks like a "dash"... of course, should ensure x/y are both > 0.

CGContextFillRect(context, CGRectMake(x - 0.5, y - 0.5, 1.0 , 1.0));

回答7:

swift 3 :

 UIRectFill(CGRect(x: x, y: y, width: 1, height: 1))