CGImage不能CIFilter圖像兩次

Question

我將過濾器應用於自定義UIImageView類中的過濾圖像，以便在設置“色相”時過濾圖像。 但是，當我調用以下代碼時，[[self image] CGImage]第一次返回正確的值。 [[self image] CGImage]周圍的第二次為零，因此CIFilter返回也為零。

有一個更好的方法嗎？

- (void)setHue:(CGFloat)aHue
{
    hue = aHue;
    NSLog( @"CG Image? %@", [[self image] CGImage] );
    CIFilter *filter = [CIFilter filterWithName:@"CIHueAdjust"];
    [filter setDefaults];
    [filter setValue:[CIImage imageWithCGImage:[[self image] CGImage]]
              forKey:@"inputImage"];
    NSLog( @"Setting new hue %f", aHue );
    [filter setValue:[NSNumber numberWithFloat:aHue] forKey:@"inputAngle"];
    [self setImage:[UIImage imageWithCIImage:[filter valueForKey:@"outputImage"]]];

    NSLog( @"Output image %@", [self image] );
}

Answer 1

UIImage可以由CGImage或CIImage來支持。 一次運行此函數並調用[UIImage imageWithCIImage] ，新的UIImage現在由CIImage支持。

這實際上很好，因為下一次此功能可以運行得更快！ 您可以簡單地檢查一下CIImage存在並直接使用它：

- (void)setHue:(CGFloat)aHue
{
    hue = aHue;
    NSLog( @"CG Image? %@", [[self image] CGImage] );
    CIFilter *filter = [CIFilter filterWithName:@"CIHueAdjust"];
    [filter setDefaults];
    if ([[self image] CGImage]) {
      [filter setValue:[CIImage imageWithCGImage:[[self image] CGImage]] forKey:@"inputImage"];
    }
    else {
      [filter setValue:[[self image] CIImage] forKey:@"inputImage"];
    }

    NSLog( @"Setting new hue %f", aHue );
    [filter setValue:[NSNumber numberWithFloat:aHue] forKey:@"inputAngle"];
    [self setImage:[UIImage imageWithCIImage:[filter valueForKey:@"outputImage"]]];

    NSLog( @"Output image %@", [self image] );
}