ios - 如何创建一个有限的 CIImage？

Question

CIColorMap CIFilter 将 CIImage 作为输入。使用另一个 CIFilter(例如 CILinearGradient)动态生成该输入图像是有意义的，但是向颜色图过滤器提供过滤器的结果将导致以下错误，例如以下内容:

[CIColorMap outputImage] requires the inputGradientImage to be finite

即使渐变的起点/终点被指定为 CILinearGradient 过滤器的输入，图像本身也不是有限的。如何生成有限的 CIImage 以传递给我的过滤器？

Answer 1

下面是一个示例，说明如何创建固定大小的 CIImage 以用作另一个 CIFilter 的输入:

CGFloat gradientSize = 100.f;         
CIFilter *gradientFilter = [CIFilter filterWithName:@"CISmoothLinearGradient"];
[gradientFilter setValue:[CIVector vectorWithX:0 Y:0] forKey:@"inputPoint0"];
[gradientFilter setValue:[CIVector vectorWithX:gradientSize Y:0] forKey:@"inputPoint1"];
[gradientFilter setValue:[CIColor colorWithCGColor:[[UIColor cyanColor] CGColor]] forKey:@"inputColor0"];
[gradientFilter setValue:[CIColor colorWithCGColor:[[UIColor magentaColor] CGColor]] forKey:@"inputColor1"];
CIImage *gradientImage = [[gradientFilter outputImage] imageByCroppingToRect:CGRectMake(0, 0, gradientSize, 1)];

// Other filter to receive cropped gradientImage
CIFilter *gradientMapFilter = [CIFilter filterWithName:@"CIColorMap"];
[gradientMapFilter setValue:gradientImage forKey:@"inputGradientImage"];