WebREAD returns zeors when reading a GIF image

I am using an Online server from NIH to convert a SMILES string to a GIF image.

This SMILES string defines a chemical structure, which is dipicted in the GIF picture.

For example, by defining the URL as https://cactus.nci.nih.gov/chemical/structure/O=c1oc2ccccc2cc1-c1cn2ccccc2n1/image this server generates a picture.

However, when I read the image using WebRead, I only get an array (250*250) of zeros .

testURL='https://cactus.nci.nih.gov/chemical/structure/O=c1oc2ccccc2cc1-c1cn2ccccc2n1/image';
myData=webread(testURL);

Does anyone know what is going wrong in this case?

How should we modify the code to retrieve the image?

Many thanks.

Answer 1

[Steve Eddins]

I got an array of zeros once using your code, but later I ran it again and got the expected image data. I quit MATLAB and launched a new session, and I got the expected image data on the first (and all subsequent) attempts.

I'm not sure, but I suspect that a server issue is causing it to sometimes send all zeros.

Also, I recommend that you use two output arguments in your call to webread. GIF files use colormaps, and you need to get the colormap to display the image correctly, like this:

testURL='https://cactus.nci.nih.gov/chemical/structure/O=c1oc2ccccc2cc1-c1cn2ccccc2n1/image';
[myData,map]=webread(testURL);
imshow(myData,map)

[Xiaogang Liu]

Dear Steve,

Many thanks for the suggestion and the great help.

I switched to another computer (on the way home). It is working now!