[Technical tips] Change the boot image of the system on i.MX series devices.

This article will tell you how to change the title logo / photo of the system for i.MX series device.
In standard image that ICOP provided; no matter it's Yocto Linux or Android, the title logo / photo is always the linux logo, but this can be changed by simple steps.
In the tips below, we will provide the guide step by step.

Tools you need:

1. i.MX series products like NX8MM-35 / PN8M-090T / EBOX-IMX8MM
   • In this tips, we use PN8M-090T as an example.
2. Yocto Linux 4.0:Recipe (Find the recipe file from our Wiki)
3. Image file of your logo / photo
4. Operating system for building the image: Ubuntu 22.04 or after

1. Making a ppm image file with 224 colors

First, prepare a custom boot image and convert it to a Linux-compatible PPM file (the image should be saved with a .ppm extension in ASCII format and have a maximum of 224 colors).
Please follow the steps below to change the image to the correct format:

1. Using pngtopnm to change the .png file to .pnm file.
    

    pngtopnm xxxx.png>linuxlogo.pnm 

   (xxxx=your file name)

   
2. pnmquant 224 to change the color to 224 colors
    

    pnmquant 224 linuxlogo.pnm>linuxlogo224.pnm

   
3. pnmtoplainpnm to change the file to change the .pnm file to .ppm file.
    

    pnmtoplainpnm linuxlogo224.pnm>logo_linux_clut224.ppm 

   

By the steps above, we can change the PNG file to 224 colors .ppm file.

2. Replace the old boot image and build the image file

In this case, we assume the user already know how to build a image file by recipe, and already has the recipe file.
If the recipe file is no implemented, check here for an example.

1. Copy the logo_linux_clut224.ppm to the logo file.
    

    cp logo_linux_clut224.ppm kernel-source/drivers/video/logo

   
     kernel-source/drivers/video/logo is the relative location, in this case, the exact location is:

    /home/user/imx-yocot-bsp/build-dmp/tmp/work-sahred/dm421/kernel-source/drivers/video/logo

   
   
   The exact location will be diffrerent based on the user's setting.
2. After replaced the logo file, run bitbake command below to compile linux-imx in the recipe after created the image setup environment. (Check step 7 ~9 here for setup environment.)
    

    bitbake -c compile -f linux-imx

   
3. Generate the image file by bitbake
    

    bitbake imx-yocto-multimedia

   

   In this case, we use imx-yocto-multimedia, the user can decide which kind of image they would like to generate; the detailed information is as below:

   Image Name	Target
   core-image-minimal	A compact image that enables the device to boot with minimal functionality.
   core-image-base	A console-only image that ensures full compatibility with the target device's hardware.
   core-image-sato	An image featuring the Sato mobile environment, providing a visual style and mobile applications such as a terminal, editor, and file manager. It utilizes the Sato theme and includes Pimlico applications.
   imx-image-core	An i.MX-based image containing i.MX test applications, designed for Wayland backends. This image is used in daily core testing for i.MX devices.
   fsl-image-machine-test	An i.MX core image from the FSL Community, providing a console-only environment with no GUI interface.
   imx-image-multimedia	An i.MX image with a graphical user interface (GUI), but without any Qt content.
   imx-image-full	An open-source Qt 5-based image that incorporates machine learning features. These images are designed specifically for i.MX SoCs with hardware graphics support and are incompatible with the i.MX 6UltraLite, i.MX 6UltraLiteLite, i.MX 6SLL, and i.MX7Dual models.

   Reference: NXP's i.MX Yocto Project User's Guide

4. Restore the image you've built to the device
   • Check How to install the image file by UUU. in the Recipe guide
   • Use the UUU to restore image (Image restore guide)
5. After restored the image to the device, you will see the boot image when booting the device