- (UIImage *)applyAlpha:(CGFloat)alpha
{
int bmpAlpha = MIN(255, MAX(0, (255*alpha)));
UIImage *image;
int width = self.size.width * self.scale;
int height = self.size.height * self.scale;
CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceRGB();
if (colorspace == NULL) {
ATLog(@"Create Colorspace Error!");
return nil;
}
Byte *imgData = NULL;
imgData = malloc(width * height * 4);
if (imgData == NULL) {
ATLog(@"Memory Error!");
CGColorSpaceRelease(colorspace);
return nil;
}
CGContextRef bmpContext = CGBitmapContextCreate(imgData, width, height, 8, width * 4, colorspace, (CGBitmapInfo)kCGImageAlphaPremultipliedLast);
if (!bmpContext) {
ATLog(@"Create Bitmap context Error!");
CGColorSpaceRelease(colorspace);
return nil;
}
CGContextDrawImage(bmpContext, CGRectMake(0, 0, width, height), self.CGImage);
for (long i = 0; i < width * height; i++) {
imgData[4*i+3] = bmpAlpha;
}
CGImageRef imageRef = CGBitmapContextCreateImage(bmpContext);
if (imageRef != NULL) {
image = [[UIImage alloc] initWithCGImage:imageRef];
CGImageRelease(imageRef);
}
CGColorSpaceRelease(colorspace);
CGContextRelease(bmpContext);
free(imgData);
return image;
}
UIimage添加分類肴甸，改變圖片透明度alpha：0.0 ~1.0 .
