CoreImage - 在CPU上运行过滤器

Question

我想在CPU上运行一些CoreImage过滤器，而不是GPU。在CI文档中，我发现您可以通过创建类似这样的上下文（see here）来表达您在CPU上执行过滤器的偏好：

NSDictionary * cpuonlycontextOptions = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool: YES],kCIContextUseSoftwareRenderer,nil];
CGContextRef cgcontext = [[NSGraphicsContext graphicsContextWithBitmapImageRep:rep] graphicsPort];
CIContext * cpu_context = [CIContext contextWithCGContext:cgcontext options: cpuonlycontextOptions];

要应用过滤器，我目前正在这样做：

NSBitmapImageRep * bitmaprep_in;
CGImageRef cg_image_in = [bitmaprep_in CGImage];

CIImage * ci_image_in = [CIImage imageWithCGImage:cg_image_in];

CIFilter * edge_filter = [CIFilter filterWithName:@"CIEdges"];
[edge_filter setDefaults];
[edge_filter setValue:ci_image_in forKey: @"inputImage"];

CIImage * result = [edge_filter valueForKey: @"outputImage"];

NSBitmapImageRep* rep = [[NSBitmapImageRep alloc]  initWithCIImage:result];

问题是，我看不到在哪里或如何设置仅CPU的CI上下文。这怎么做得好？

Answer 1

这会强制CPU渲染：

NSDictionary *theCIContextOptions = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], kCIContextUseSoftwareRenderer, NULL];

CIContext *theCIContext = [CIContext contextWithOptions:theCIContextOptions ];