When drawing a pixel, also the pixel above is impacted

[woutervanh]

We are running cog on a imx53, using mainline linux + freedreno / mesa.
We have an application where we need to have the output exactly as we draw it on the canvas. However there seems to be something off there. It seems that single pixels also impacts the pixel above. This is not noticeable when we take a screenshot using inspector, but is visible when we make a screenshot using weston-screenshooter. Dithering is already (hard) disabled in freedreno. We need this pixels exactly because these are interpreted by a fpga, connected via the parallel display output.

I already did some things trying to disable aliasing in webkit/cairo (as I thought that might be the culprit), but it doesn't help me out.

Does anyone has an idea?

Illustration of what I mean. Upper is as expected and exported using inspector, lower is as captured by screenshooter (and read out via fpga) Row is one pixel high:

screenshot

[woutervanh]

Opened issue with Cog itself.
Igalia/cog#636
Nevertheless, if anyone has an idea, please let me know