I read a table with 64 features, create a collection column of them, convert it to an image, and try to write this image. The image writing doesn’t work.
Warnings like this usually indicate that there may be a more detailed message logged to the KNIME log. Indeed, the error message (stack trace) in the log said that the pixel type (Int) can’t be written in the .jpeg format. Depending on the range of your values you could convert your images to UNSIGNEDBYTETYPE, which should be writable in most of the formats (assuming your values are not higher than 255). This can be easily done in the configuration of the Data Row to Image node at the bottom. However, there seems to be a problem with the naming of the Dimension Labels. You have to change them to upper case, otherwise the Image Writer node will throw an error. We’ll look into that.