I'm using digikam to batch convert photos to black & white (sepia) from the album "a" to a new album "b".
It processes the images in the batch queue. The resulting images are full black without any white or gray.
Black & white images as resulting from the single image conversion by the showfoto single image process.
Steps to reproduce:
1. Open a new batch queue in digikam.
2. Select any images to process.
3. Select the black & white conversion tool.
4. Choose any parameters - i.e. the default ones.
5. Run the batch process. - Here you are.
Same behaviour detected on kubuntu with digikam 2.8.0
*** This bug has been marked as a duplicate of bug 281095 ***
Fixed with #281095