Yocto + Qt5 + LVDS on i.MX6 (FSL Community BSP): rendering and color depth

[daheronj]

I've made my own yocto image for a Udoo neo board using graugans/meta-udoo, in eglfs mode (no X11 / Wayland), following this tutorial : http://wiki.wandboard.org/index.php/Building_Qt5_using_yocto_on_Wandboard
Then I developped a simple QT5 application displayed on Udoo's 7" LVDS display.
The rendering of my image is not correct. It seems to be displayed in R/G/B/A = 4/4/4/0 instead of 6/6/6/0.
How can I specify this values before launchning my application ?
Moreover, transparency is not correctely managed on LVDS (but works fine on my PC), could it be a matter with ALPHA value ?

I launch my application by running this script :

#!/bin/sh
export QT_QPA_PLATFORM=eglfs
export QT_QPA_EGLFS_DEBUG
/home/root/my_app

Application logs :

root@udooneo:~# ./launch
Created context for format QSurfaceFormat(version 2.0, options QFlags(), depthBufferSize 0, redBuffe
rSize 4, greenBufferSize 4, blueBufferSize 4, alphaBufferSize 0, stencilBufferSize 0, samples 0, swa
pBehavior 0, swapInterval 1, profile  0) with config:
        EGL_BUFFER_SIZE: 12
        EGL_ALPHA_SIZE: 0
        EGL_BLUE_SIZE: 4
        EGL_GREEN_SIZE: 4
        EGL_RED_SIZE: 4
        EGL_DEPTH_SIZE: 0
        EGL_STENCIL_SIZE: 0
        EGL_CONFIG_CAVEAT: 12344
        EGL_CONFIG_ID: 1
        EGL_LEVEL: 0
        EGL_MAX_PBUFFER_HEIGHT: 8064
        EGL_MAX_PBUFFER_PIXELS: 65028096
        EGL_MAX_PBUFFER_WIDTH: 8064
        EGL_NATIVE_RENDERABLE: 0
        EGL_NATIVE_VISUAL_ID: 0
        EGL_NATIVE_VISUAL_TYPE: 12344
        EGL_SAMPLES: 0
        EGL_SAMPLE_BUFFERS: 0
        EGL_SURFACE_TYPE: 1285
        EGL_TRANSPARENT_TYPE: 12344
        EGL_TRANSPARENT_BLUE_VALUE: -1
        EGL_TRANSPARENT_GREEN_VALUE: -1
        EGL_TRANSPARENT_RED_VALUE: -1
        EGL_BIND_TO_TEXTURE_RGB: 1
        EGL_BIND_TO_TEXTURE_RGBA: 1
        EGL_MIN_SWAP_INTERVAL: 0
        EGL_MAX_SWAP_INTERVAL: 10

Many thanks,