Minor bug in Graphics.drawImage()

[espruino-discuss3]

Posted at 2020-10-29 by SergeP

Hi!
I've just tried to write an image to my famous clock :) and found a bug with transparent color.

var image={ width:9 , height:13 , bpp:24 ,
  buffer:Uint24Array(
[
  0x0,0x1,0x2,0x4,0x8,0x10,0x20,0x40,0x80,
  0x0,0x100,0x200,0x400,0x800,0x1000,0x2000,0x4000,0x8000,
  0,0,0,0,0,0,0,0,0,
  0,0,0,0,0,0,0,0,0,
  0x0,0x10000,0x20000,0x40000,0x80000,0x100000,0x200000,0x400000,0x800000,
]),
  transparent: 0x1,
};
gt.drawImage(image, 5, 1);
neopixel.write(pin, gt.buffer);

I expect transparent point is in first image line (I can find it even if image is mirrored because there is second color line near) but it is actually in last one. If I set transparent to 0x10000 I see transparent point in first line while expect it in last one.

[gfwilliams]

Posted at 2020-10-29 by @gfwilliams

Ahh - I believe this may be related to how multi-byte pixels are interpreted in images. I think they're big endian while the Uint24Array is little endian?