In order to solve this, the decoded image should not be a simple pointer of img_data but a complete draw_buf with decoded area.

#4833

img_decode_and_draw should check if the area to be draw has already been decoded or not.

/**Describe an image decoding session. Stores data about the decoding*/
typedef struct _lv_image_decoder_dsc_t {
    /**The decoder which was able to open the image source*/
    lv_image_decoder_t * decoder;

    /*A copy of parameters of how this image is decoded*/
    lv_image_decoder_args_t * args;

    /**The image source. A file path like "S:my_img.png" or pointer to an `lv_image_dsc_t` variable*/
    const void * src;

    /** Pointer to a buffer where the image's data (pixels) are stored in a decoded, plain format.
     *  MUST be set in `open` function*/
    const uint8_t * img_data;
   
    ...
} lv_image_decoder_dsc_t;

A similar issue is for indexed image, it could decode to ARGB8888 image, which makes it inconsistent with header->cf. Adding lv_draw_buf_t decoded could also solve it. Decoded format could differ to original format.

I currently hacked the code to mark img_data as NULL, so to continue debug CI test fail issues.

I don't think it's hacky, but rather a good clean up.

A similar issue is for indexed image, it could decode to ARGB8888 image, which makes it inconsistent with header->cf. Adding lv_draw_buf_t decoded could also solve it. Decoded format could differ to original format.

The header here should store data for the decoded image.

However considering it a lv_draw_buf_t decoded_image is definitely more elegant. Let's go for it!

The header here should store data for the decoded image.

If so, then get_area_cb will get lost because it should deal with indexed image for example, not ARGB8888.

It could use const void * src; to read the original color format. However I do agree to add lv_draw_buf_t decoded_image it's much less hacky.

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Will be fixed in #4948, close it for now.