drawBitmap() not always working...

[exdiogene]

I was trying to enhance the solution for image drawing proposed in this discussion :

#160

The solution provided by "e-labInnovations" is a very slow process taking more than 900mS to display a 256 X 256 picture.

I had better performance using this code instead of his :

      r = ((my_data >> 11) & 0x1F) << 3;   // red   0 .. 255
      g = ((my_data >> 5) & 0x3F) << 2;  // green 0 .. 255
      b = (my_data & 0x1F) << 3;         // blue  0 .. 255

But it still take 630mS to display the picture!

So I tried to convert a line_array to a Bitmap_array to accelerate the process :

    png.getLineAsRGB565(pDraw, bpm_data2, PNG_RGB565_LITTLE_ENDIAN, 0xffffffff);
    for (int16_t i = 0; i < pDraw->iWidth; i++) {
      my_data = bpm_data2[i];
      r = ((my_data >> 11) & 0x1F) << 3;   // red   0 .. 255
      g = ((my_data >> 5) & 0x3F) << 2;  // green 0 .. 255
      b = (my_data & 0x1F) << 3;         // blue  0 .. 255
      myBitmap_data[(i * 4)] = r;
      myBitmap_data[(i * 4) + 1] = g;
      myBitmap_data[(i * 4) + 2] = b;
      myBitmap_data[(i * 4) + 3] = 0xff;
    }
    Bitmap myBitmap = Bitmap(pDraw->iWidth, 1, &myBitmap_data[0], PixelFormat::RGBA8888);
    canvas.drawBitmap(0,pDraw->y,&myBitmap);

Now the process take only 65mS to display the picture, but the picture is partially displayed between 20% to 50% vertically...

Some horizontal lines get lost in the process, probably due by the VGA synchronization process, is there a way to display the missing lines correctly?

The only found solution at the moment is to put a "canvas.waitCompletion(false);" after the drawBitmap(), but it increase the process to 120mS.

I tried to put the "canvas.waitCompletion(false);" before the drawBitmap(), but it create some garbage in my picture, do you know why?

Any answer would be greatly appreciated...

[exdiogene]

I was able to reduce the time to 88mS by converting the Bitmap_array to the PixelFormat RGBA2222.

Now I wonder about the way to construct a Color Palette while proceeding the bytes in the array, my images have less than 16 colors. Is it possible to have a hint how to create and use a Palette with "drawBitmap()"?