使用驱动程序版本 275.50 和 280.19 为 Nvidia GTX480 GPU 重新采样图像在灰度值上几乎没有变化。也许这是一个插值问题。除了实施 OpenCL 1.1 版之外，我无法确定新版本中发生了什么变化。仅使用 OpenCL 1.0 会在灰度值上产生相同的微小变化。
下面是在驱动程序版本 275.50 和 280.19 之间给出不同结果的代码：
success oclInitImgData(struct _Image2d *image)
{
cl_image_format volume_format;
volume_format.image_channel_order = CL_R;
volume_format.image_channel_data_type = CL_UNORM_INT16;
size = len[0] * sizeof(unsigned short);
img_h = clCreateImage2D(Ocl._GPUContext, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR,
&volume_format, len[0], len[1], size, data, &error);
resampledImg_h = clCreateBuffer(Ocl._GPUContext, CL_MEM_READ_WRITE, size, NULL, &error);
oclResampleImg(Ocl._GPUCommandQueue[posSet], Ocl._pGPUKernels[posSet][K_IMG_RESAMPLE], img_h, resampledImg_h , Size, PixelSize, mm_per_p, vm_h);
}
__kernel void resampleImage( __read_only image2d_t IN image, __global uint OUT *resampledImage)
{
//get resampled position
int2 posResampledImg = (int2)(get_global_id(0), get_global_id(1));
//get dimension of the image
int2 imageSize = get_image_dim(image);
//calulate image size in mm
float2 imageSizemm = convert_float2(imageSize)*imagePixelSize;
float2 posImg = (posResampledImgmm + (imageSizemm*0.5f));
float2 posImgnorm = posImg/imageSizemm;
int2 posImgpix = convert_int2(posImg/imagePixelSize);
uint sample = 0;
if(read_imageui(image, CLK_NORMALIZED_COORDS_FALSE | CLK_ADDRESS_CLAMP | CLK_FILTER_NEAREST, posImgpix).x == 1)
{
//get grey value and store it in the resampled image
sample = read_imagef(image, CLK_NORMALIZED_COORDS_TRUE | CLK_ADDRESS_CLAMP | CLK_FILTER_LINEAR, posImgnorm).x * 65535.0f;
}
resampledImg[posResampledImg.y*convert_int(imageSizeResampled.x)+posResampledImg.x] = sample;
}