imresize error. "Expected input method to be a string or a character vector. Allowed values are: 'cubic' or 'bicubic'."

I get the error message:

Expected input method to be a string or a character vector. Allowed values are:
'cubic' or 'bicubic'.

when running the following code:

scale = delta1/delta2; 
Image_scaled = imresize(Image, scale, 'bilinear'); 

Strangely, this error happens only when I run the code on a GPU server, but not on a CPU. Do you have any idea what is causing this error? I do not want to use cubic or bicubic interpolation in my code.

Note that the variable 'Image' is a gpuArray, and I also get the warning message:

Warning: The CUDA driver must recompile the GPU libraries because your device is more recent than the libraries. Recompiling can take several minutes.
  In parallel_function>make_general_channel/channel_general (line 837)
  In remoteParallelFunction (line 46)

Answer 1

[Daigo]

I could solve this problem by retrieving the array from the GPU by gather function.

grayImage = gather(gpu_grayImage); 
grayImage_scaled = imresize(grayImage, scale, 'bilinear'); 

Answer 2

[Alex Taylor]

If you look at the documentation for previous versions of MATLAB, under the Extended Capabilities section for gpuArray in the imresize doc, there is a note that only bicubic interpolation was supported for gpuArray/imresize in R2020b and previous versions:

https://www.mathworks.com/help/releases/R2020b/matlab/ref/imresize.html?searchHighlight=imresize&s_tid=doc_srchtitle

In R2021a and later the full set of interpolants work for gpuArray inputs.

[Daigo]

Thank you for your follow-up, Alex! I was missing the note in the documentation. This section will be helpful when I need to check the limitations of other functions as well. Thank you for pointing out!

Answer 3

[Image Analyst]

First of all, it's probably not a good idea to call your variable Image since image() is a built-in function. I know one is capital and one is not, but still, I would not recommend it.

What is delta1 and delta2? Take the semicolon off and see what the value is. Might scale be an array?

Does the code below work for you?

grayImage = imread('moon.tif');
whos grayImage

  Name             Size              Bytes  Class    Attributes

  grayImage      537x358            192246  uint8              

subplot(1, 2, 1);
imshow(grayImage);
axis('on', 'image')
delta1 = 3

delta1 = 3

delta2 = 50

delta2 = 50

scale = delta1/delta2

scale = 0.0600

whos scale

  Name       Size            Bytes  Class     Attributes

  scale      1x1                 8  double              

smallImage = imresize(grayImage, scale, 'bilinear');
subplot(1, 2, 2);
imshow(smallImage);
axis('on', 'image')

[Daigo]

Hi, thank you for your answer! Actually your code worked but not for my input image. The problem was due to the gpuArray. It seems like the imresize function does not work properly for the gpuArray input.