Scratches on visualization related to opacity setting


Hello, I am developing an application based on the NXP MiMX1052RT processor, embedded on a custom board and a custom color LCD display 320x240. I use MCU-Expresso with GuiGuider 1.7.0.-GA and LVGL version 8.3.10. All the toolchain works fine, but I have an issue in visualizing widget with rounded shapes on the display: all the boarders are stable and OK, while the internal colors appears to be scrached (see pictures enclosed). I am pretty sure all the hardware settings to the display are OK (16bit RGB, double frame buffer scheme, 52Hz refresh rate) since: - I send only one frame to the display, and - all the syncronization signals are present and clean, with the correct frame rate - the image remains stable - the colors are fine But the image is corrupted in the fillings. I believe that there is something odd with the blending between the image and the alpha channel, since if I modify slightly the opacity setting (from 100% to 98%) the image get sharply worst (see pictures). Another thing to note is that also images (not shown in the example enclosed) are affected by this if I set the attribute True Color Alpha on GuiGuider, while they are perfect if I set True Color only. I have tried a lot of things, but nothing worked.

I discovered that if I put on top a transparent image all the background widgets are drawn correctly. This supports the theory that there is something odd with opacity settings. See “Image Custom Display - top transparency.jpg”.

Thank you!

What MCU/Processor/Board and compiler are you using?

NXP MiMX1052RT, MCUXpresso IDE v11.8.0 with GCC, GuiGuider 1.7.0.-GA

What LVGL version are you using?


What do you want to achieve?

To have widget correctly shown without tricks

What have you tried so far?

I tried changing widget opacities, some lv_conf.h parameters, antialiasing, background color and properties, images in TrueColor and not.

Code to reproduce

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Screenshot and/or video