metal performance shader 实现直方图均衡化，直方图计算部分没问题，到了执行 encodeTransformToCommandBuffer 计算累加直方图的时候报错.

metal performance shader 实现直方图均衡化，直方图计算部分没问题，到了执行 encodeTransformToCommandBuffer 计算累加直方图的时候报错： -[MTLDebugComputeCommandEncoder setBuffer:offset:atIndex:]:283: failed assertionoffset(4096) must be < buffer length.'`

代码:

// histogram
        MPSImageHistogramInfo info;
        info.histogramForAlpha = true;
        info.numberOfHistogramEntries = 256;
        info.minPixelValue = simd_make_float4(0, 0, 0, 0);
        info.maxPixelValue = simd_make_float4(1, 1, 1, 1);
        MPSImageHistogram *histogram = [[MPSImageHistogram alloc] initWithDevice:_device histogramInfo:&info];
        size_t length = [histogram histogramSizeForSourceFormat:sourceTexture.pixelFormat];
        id<MTLBuffer> histogramInfoBuffer = [_device newBufferWithLength:length options:MTLResourceStorageModePrivate];
        [histogram encodeToCommandBuffer:commandBuffer sourceTexture:sourceTexture histogram:histogramInfoBuffer histogramOffset:0];
        
        MPSImageHistogramEqualization *equalization = [[MPSImageHistogramEqualization alloc] initWithDevice:_device histogramInfo:&info];
        // accumulative distribution function of the histogram
        [equalization encodeTransformToCommandBuffer:commandBuffer sourceTexture:sourceTexture histogram:histogramInfoBuffer histogramOffset:0];
        // apply equalisation
        [equalization encodeToCommandBuffer:commandBuffer sourceImage:sourceTexture destinationImage:destTexture];