iOS：如何从CGContextRef中检索图像尺寸X，Y

As it says on the can; here is an example of why I need it:

正如它在罐头上所说;这是我需要它的一个例子:

Let's say I create a bitmap context:

假设我创建了一个位图上下文:

size_t pixelCount = dest_W * dest_H;

typedef struct {
    uint8_t r,g,b,a;
} RGBA;

// backing bitmap store
RGBA* pixels = calloc( pixelCount, sizeof( RGBA ) );

// create context using above store
CGContextRef X_RGBA;
{
    size_t bitsPerComponent = 8;
    size_t bytesPerRow = dest_W * sizeof( RGBA );

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    // create a context with RGBA pixels
    X_RGBA = CGBitmapContextCreate( (void *)pixels, dest_W, dest_H, 
                                   bitsPerComponent, bytesPerRow, 
                                   colorSpace, kCGImageAlphaNoneSkipLast
                                   );        
    assert(X_RGBA);

    CGColorSpaceRelease(colorSpace);
}

Now I want to throw this context to a drawing function that will eg draw a circle touching the edges:

现在我想把这个上下文抛给一个绘图函数,例如绘制一个接触边缘的圆圈:

Do I really need to throw in the width and height as well? I am 99% sure I have seen some way to extract the width and height from the context, but I can't find it anywhere.

我是否真的需要投入宽度和高度?我99%肯定我已经看到从上下文中提取宽度和高度的某种方法,但我无法在任何地方找到它。

1 个解决方案

#1

CGBitmapContextGetWidth // and Height

NB width and height probably don't make sense to a non-bitmap CGContextRef

NB宽度和高度可能对非位图CGContextRef没有意义

Thanks @ wiliz on #iphonedev

谢谢@ wiliz在#iphonedev上

#1

CGBitmapContextGetWidth // and Height