cocoa - 与[CIContext绘制图像:…]

Question

最后两行有什么区别？

    CIImage *outputImage = [compositingFilter valueForKey:@"outputImage"];


    [[[NSGraphicsContext currentContext] CIContext] drawImage:outputImage atPoint:point fromRect:fromRect];

    [outputImage drawAtPoint:point fromRect:fromRect operation:op fraction:delta];

最后一个生成一个扭曲的图像，其矩形小于[outputImage范围]；

drawImage: 线在某些情况下会崩溃。

Answer 1

来自 -drawAtPoint 的文档:...

The image content is drawn at its current resolution and is not scaled unless the CTM of the current coordinate system itself contains a scaling factor. The image is otherwise positioned and oriented using the current coordinate system.

如果您想要绘制整个图像，fromRect 应该是图像的整个大小。此外，在许多情况下，不同绘图方法之间的翻转处理方式也不同。

最后，-drawImage 上的文档:...有些神秘地仅说明:

You can call this method to force evaluation of the result after you apply a filter using one of the methods of the CIFilter class, such as apply:, apply:arguments:options:, and apply:k…

希望这有帮助。