ios 如何使用 Core Graphics 绘制点？
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How do I draw a point using Core Graphics?
提问by
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?
我在 Quartz 中看到了用于绘制线条和圆形的 API。但我想要做的就是指定 (x,y) 笛卡尔坐标以将像素着色为特定值。我怎么做？
回答by
CGContextFillRect(context, CGRectMake(x,y,1,1));
回答by Jens Ayton
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 CGImagefrom the same buffer using CGImageCreate()and drawing that.
Quartz 不是面向像素的 API，它的上下文不一定是像素缓冲区。如果要绘制像素图，请使用CGBitmapContextCreate(). 你提供了一个缓冲区，你可以直接操作它，并且可以通过CGImage使用CGImageCreate()和绘制它从同一个缓冲区创建一个来复制到另一个上下文。
回答by Paulo
Draw a very small ellipse/circle and fill it!
画一个非常小的椭圆/圆并填充它！
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.
我正在使用此代码在带点音符的音符中创建一个小点（3x3 像素）。
回答by Chad
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.
将线帽设置为 kCGLineCapRound 后，我得到了一个要绘制的点（零长度线）。默认线帽没有长度，因此无法绘制。
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.
点没有大小的论点是愚蠢的。线条没有宽度，但我们可以绘制它们（通过使用绘制状态中的“线条宽度”）。一个点应该以完全相同的方式绘制，并且我相信它可以使用不同的线帽。
Maybe this behavior is new?
也许这种行为是新的？
回答by Ben Gottlieb
You can draw a 1-pixel-length line at the coordinate in question; that should accomplish what you want.
您可以在相关坐标处绘制一条 1 像素长的线；这应该完成你想要的。
回答by Ben Gottlieb
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.
我遇到了同样的问题 - 我发现最好的解决方案与最后一个类似，但至少它不会留下看起来像“破折号”的东西......当然，应该确保 x/y 都 > 0 .
CGContextFillRect(context, CGRectMake(x - 0.5, y - 0.5, 1.0 , 1.0));
CGContextFillRect(context, CGRectMake(x - 0.5, y - 0.5, 1.0, 1.0));
回答by Antoine Weber
swift 3 :
快速3：
UIRectFill(CGRect(x: x, y: y, width: 1, height: 1))
