Dithering not working on some PNG images

[MAW0914 (Mike W.)]

Hi. I have spent a lot of time working on getting the xTool D1 5w to replicate a specific grayscale photo using Jarvis method on .09" basswood and I have finally achieved perfect results.

But- after attempting to get the same outcome on some PNGs I made in a drawing program, those images consistently fail to show any kind of dithering, even with all the exact same settings and similar black levels as the first image (all images are black and white).

Both images were exported out of the same program into the same format after editing.

The only main differences between the two is the first image was originally a photo edited in Photoshop then further edited in a separate program with no added transparencies; while the other images were created with drawing tools consisting of both vector and raster layers with added transparencies, masks and changes to opacity.

I have tried enabling pass-through but it made no difference. I tested the machine on a tiny gradient and it did a great job with that. So I decided to export the problem images into JPEGs instead and it finally started to show the more transparent parts of the image.

Being that my first image was a PNG that came out great, why could have the other images not worked so well until converted to a different format?

[LightBurn (Oz)]

I suspect the image is either completely black or completely white, with all of the image data in the transparency layer, instead of being an image with transparency used to dictate which parts aren’t visible. I’ve seen this before, and it breaks the dithering code in LightBurn, because it’s only using the transparency information to figure out which parts of the image should be kept.

[MAW0914 (Mike W.)]

Interesting. Well all my images consist of multiple layers which are mainly just brush strokes with masks fading out certain parts. I thought formats like JPEG and PNG were pretty much interpreted the same way.

Should I try converting all my layers into one raster layer or simply stick to JPEG? As far as I can tell Lightburn treats them both the same otherwise, as long as I have an empty background on my image.