Unfinished spike to load PNG via HTTP and display on e-Paper display with ESP32

epaper_http_png.cpp

/*

Unfinished spike to load PNG via HTTP and display on e-Paper display with ESP32.

Please fill in teh gaps. Currently, it will probably not even compile.

The primitives have been taken from:
- https://github.com/lagunax/ESP32-upng
- https://github.com/ZinggJM/GxEPD2/blob/master/examples/GxEPD2_GFX_Example/BitmapDisplay.cpp
*/

// Acquire PNG image using HTTP.
const unsigned png_buffer* = <fetch with http>;
const int_8 png_length = 3000;

// Read PNG image.
upng_t* upng;
upng = upng_new_from_bytes(png_buffer, png_length);

if (upng != NULL) {
    
    // Decode PNG image.
    upng_decode(upng);
    if (upng_get_error(upng) == UPNG_EOK) {

        // Get pointer to bitmap buffer.
        const uint8_t *bitmap = upng_get_buffer(upng);

        // Display bitmap on e-Paper.
        //display.fillScreen(GxEPD_WHITE);
        display.writeScreenBuffer(); // use default for white

        display.drawImage(bitmap, 0, 0, 200, 200, false, false, true);
        //display.writeImage(bitmap, 0, 0, 200, 200, false, false, true);
        display.refresh(true);

    }

    upng_free(upng);
}