PNGs are all black


I’ve exported my images form and the PNGs are all black and I cannot see any labels. Did this happen to anyone else? Do you know of any solutions for this?


Hi Elisa,

yes, this is a well-known problem. Here is why it happens: for each pixel we store which class it belongs to. We store 0 as pixel-value for the background, 1 if it belongs to class 1, 2 for class 2, …

However, if you display this as a grey-scale picture the pixel-values are interpreted as brightness; 0 is the darkest (=black) and 255 the brightest (=white). On this scale, the human eye can’t see the difference between two values next to each other (e.g., 1 and 2), and therefore, it all appears to be black. A CNN, on the other hand, could tell the difference.

We also offer the option to encode the annotations to different colors in the export menu. If you choose to do this, make sure to adjust your model accordingly when training it though.

All the best,