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问题

我第一次尝试性能着色器并遇到了运行时问题。返回的MTLTexture似乎MTKTextureLoader与 Metal Performance Shaders 的MPSImageFindKeypoints编码器不兼容。

到目前为止，我发现的唯一提示来自 @warrenm 在 MPS 上的示例代码，它MTKTextureLoaderOptions像我一样指定。我没有在文档中找到任何其他提及。

非常感谢任何帮助。

错误

/BuildRoot/Library/Caches/com.apple.xbs/Sources/MetalImage/MetalImage-121.0.2/MPSImage/Filters/MPSKeypoint.mm:166: failed assertion `Source 0x282ce8fc0 texture type (80) is unsupported

其中 0x282ce8fc0MTLTexture来自纹理加载器。据我所见，没有 MTLTexture 类型 80，枚举范围高达 8 左右（不是十六进制）。

代码

CGFloat w = CGImageGetWidth(_image);
CGFloat h = CGImageGetHeight(_image);
id<MTLDevice> device = MTLCreateSystemDefaultDevice();
id<MTLCommandQueue> commandQueue = [device newCommandQueue];

NSDictionary* textureOptions = @{ MTKTextureLoaderOptionSRGB: [[NSNumber alloc] initWithBool:NO] };
id<MTLTexture> texture = [[[MTKTextureLoader alloc] initWithDevice:device] newTextureWithCGImage:_image
                                                                                         options:textureOptions
                                                                                           error:nil];
id<MTLBuffer> keypointDataBuffer;
id<MTLBuffer> keypointCountBuffer;

MTLRegion region = MTLRegionMake2D(0, 0, w, h);

id<MTLCommandBuffer> commandBuffer = [commandQueue commandBuffer];
MPSImageKeypointRangeInfo rangeInfo = {100,0.5};
MPSImageFindKeypoints* imageFindKeypoints = [[MPSImageFindKeypoints alloc] initWithDevice:device
                                                                                     info:&rangeInfo];
[imageFindKeypoints encodeToCommandBuffer:commandBuffer
                            sourceTexture:texture
                                  regions:&region
                          numberOfRegions:1
                      keypointCountBuffer:keypointCountBuffer
                keypointCountBufferOffset:0
                       keypointDataBuffer:keypointDataBuffer
                 keypointDataBufferOffset:0];

[commandBuffer commit];

NSLog(keypointCountBuffer);
NSLog(keypointDataBuffer);

编辑

将图像转换为正确的像素格式后，我现在正在初始化缓冲区，如下所示：

id<MTLBuffer> keypointDataBuffer = [device newBufferWithLength:maxKeypoints*(sizeof(MPSImageKeypointData)) options:MTLResourceOptionCPUCacheModeDefault];
id<MTLBuffer> keypointCountBuffer = [device newBufferWithLength:sizeof(int) options:MTLResourceOptionCPUCacheModeDefault];

没有错误了。但是我现在如何阅读内容？

((MPSImageKeypointData*)[keypointDataBuffer contents])[0].keypointCoordinate为所有索引返回 (0,0)。我也不知道怎么读keypointsCountBuffer。转换为 int 值的缓冲区内容显示的值高于定义的 maxKeypoints。我看不到文档在哪里说计数缓冲区具有哪种格式。

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1 回答 1

4

最后代码正在运行，为了完整起见，我认为我应该发布整个代码作为答案

代码

id<MTLDevice> device = MTLCreateSystemDefaultDevice();
id<MTLCommandQueue> commandQueue = [device newCommandQueue];

// init textures
NSDictionary* textureOptions = @{ MTKTextureLoaderOptionSRGB: [[NSNumber alloc] initWithBool:NO] };
id<MTLTexture> texture = [[[MTKTextureLoader alloc] initWithDevice:device] newTextureWithCGImage:_lopoImage
                                                                                         options:textureOptions
                                                                                           error:nil];
MTLTextureDescriptor *descriptor = [MTLTextureDescriptor texture2DDescriptorWithPixelFormat:(MTLPixelFormatR8Unorm) width:w height:h mipmapped:NO];
descriptor.usage = (MTLTextureUsageShaderRead | MTLTextureUsageShaderWrite);
id<MTLTexture> unormTexture = [device newTextureWithDescriptor:descriptor];

// init arrays and buffers for keypoint finder
int maxKeypoints = w*h;
id<MTLBuffer> keypointDataBuffer = [device newBufferWithLength:sizeof(MPSImageKeypointData)*maxKeypoints options:MTLResourceOptionCPUCacheModeWriteCombined];
id<MTLBuffer> keypointCountBuffer = [device newBufferWithLength:sizeof(int) options:MTLResourceOptionCPUCacheModeWriteCombined];

MTLRegion region = MTLRegionMake2D(0, 0, w, h);

// init colorspace converter
CGColorSpaceRef srcColorSpace = CGColorSpaceCreateWithName(kCGColorSpaceSRGB);
CGColorSpaceRef dstColorSpace = CGColorSpaceCreateWithName(kCGColorSpaceLinearGray);

CGColorConversionInfoRef conversionInfo = CGColorConversionInfoCreate(srcColorSpace, dstColorSpace);
MPSImageConversion *conversion = [[MPSImageConversion alloc] initWithDevice:device
                                  srcAlpha:(MPSAlphaTypeAlphaIsOne)
                                 destAlpha:(MPSAlphaTypeNonPremultiplied)
                           backgroundColor:nil
                            conversionInfo:conversionInfo];

// init keypoint finder
MPSImageKeypointRangeInfo rangeInfo = {maxKeypoints,0.75};
MPSImageFindKeypoints* imageFindKeypoints = [[MPSImageFindKeypoints alloc] initWithDevice:device
                                                                                     info:&rangeInfo];

// encode command buffer
id<MTLCommandBuffer> commandBuffer = [commandQueue commandBuffer];
[conversion encodeToCommandBuffer:commandBuffer sourceTexture:texture destinationTexture:unormTexture];
[imageFindKeypoints encodeToCommandBuffer:commandBuffer
                            sourceTexture:unormTexture
                                  regions:&region
                          numberOfRegions:1
                      keypointCountBuffer:keypointCountBuffer
                keypointCountBufferOffset:0
                       keypointDataBuffer:keypointDataBuffer
                 keypointDataBufferOffset:0];

// run command buffer
[commandBuffer commit];
[commandBuffer waitUntilCompleted];

// read keypoints
int count = ((int*)[keypointCountBuffer contents])[0];
MPSImageKeypointData* keypointDataArray = ((MPSImageKeypointData*)[keypointDataBuffer contents]);
for (int i = 0 ; i<count;i++) {
    simd_ushort2 coordinate = keypointDataArray[i].keypointCoordinate;
    NSLog(@"color:%f | at:(%u,%u)", keypointDataArray[i].keypointColorValue, coordinate[0], coordinate[1] );
}

我想应该有一种更聪明的方法来分配关键点缓冲区，[device newBufferWithBytesNoCopy]这样您就不需要将内容复制回分配的数组中。它只是没有弄清楚正确对齐缓冲区。

另外我应该提一下，我猜通常在任何类型的特征检测之后你都会有一个灰度纹理，这样就不需要图像转换部分了。

于 2018-10-12T09:33:25.077 回答