0
即使视图的.alpha属性设置为非1值,我也需要获取视图快照的完全不透明版本。获取未应用视图快照的视图快照
我通过快速快照获取iOS中7我的快照:
UIGraphicsBeginImageContextWithOptions(size, NO, 0.0f);
[self drawViewHierarchyInRect:CGRectMake(0, 0, size.width, size.height) afterScreenUpdates:NO];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
我期待在这个转换为位图数据,并通过1修改所有的α值的 - view.alpha。我认为这会工作,但我需要获得非预乘位图数据。
CGContextRef context = NULL;
CGColorSpaceRef colorSpace;
uint32_t *bitmapData;
size_t bitsPerPixel = 32;
size_t bitsPerComponent = 8;
size_t bytesPerPixel = bitsPerPixel/bitsPerComponent;
size_t width = CGImageGetWidth(image);
size_t height = CGImageGetHeight(image);
size_t bytesPerRow = width * bytesPerPixel;
size_t bufferLength = bytesPerRow * height;
colorSpace = CGColorSpaceCreateDeviceRGB();
if(!colorSpace) {
NSLog(@"Error allocating color space RGB\n");
return NULL;
}
// Allocate memory for image data
bitmapData = (uint32_t *)malloc(bufferLength);
if(!bitmapData) {
NSLog(@"Error allocating memory for bitmap\n");
CGColorSpaceRelease(colorSpace);
return NULL;
}
//Create bitmap context
context = CGBitmapContextCreate(bitmapData,
width,
height,
bitsPerComponent,
bytesPerRow,
colorSpace,
(kCGBitmapAlphaInfoMask & kCGImageAlphaLast)); //RGBA
除非有更简单的方法去了解这一点,我为什么不能得到kCGImageAlphaLast工作? kCGImageAlphaPremultipliedLast似乎工作,但这不会工作。
<Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; kCGImageAlphaLast; 8192 bytes/row.