[CS6-CC2018][MAJOR BUG] Images upscaled in flattened PDF-files when placed over gradient
With this post I would like to report a major bug in Indesign.
The problem occurs in these conditions:
- A gradient background
- On top of the background product images containing clipping masks / transparency. The images have insufficiënt resolution (105ppi).
When creating a flattened PDF-file (1.3) using the default PDF export feature, and valid high resolution export presets, all images which have a resolution higher then 75ppi, are upscaled in the final PDF-file. Images which are 105 ppi, are suddenly 300ppi in the final PDF-file. Images which an effection resolution of 75 ppi, remain 75 ppi.
After doing some tests, the resolution value entered in the "Gradient and mesh resolution" field located in the flattener presets, seems to be used when flattening the file.
This becomes a big issue when trying to validate PDF-files using Acrobat Preflight, Pitstop, Pitstop server or any other workflow solution. Low resolution images are no longer detected as low resolution and are passing trough any PDF workflow validation process.
This issue could be replicated all to way back to version CS6.
Indesign should never upscale images and always keep the original resolution, as long it doesn't exceed the max resolution defined in the PDF-export setting. If flattening should occur, it should generate images which have a resolution equal to the resolution of the images which has the lowest resolution, located in that same location.