Galactic Unicorn: Displaying jpeg files

Support
1

I have been trying to get the Galactic Unicorn to display various small, non-progressive jpeg files using the following code, but I can’t seem to get it to work. Any idea why ?

from picographics import PicoGraphics, PEN_RGB332, DISPLAY_GALACTIC_UNICORN as DISPLAY
from galactic import GalacticUnicorn
import jpegdec

galactic = GalacticUnicorn()
graphics = PicoGraphics(DISPLAY)

def pressed():
    if galactic.is_pressed(GalacticUnicorn.SWITCH_A):
        return GalacticUnicorn.SWITCH_A
    if galactic.is_pressed(GalacticUnicorn.SWITCH_B):
        return GalacticUnicorn.SWITCH_B
    if galactic.is_pressed(GalacticUnicorn.SWITCH_C):
        return GalacticUnicorn.SWITCH_C
    if galactic.is_pressed(GalacticUnicorn.SWITCH_D):
        return GalacticUnicorn.SWITCH_D
    return None

display = PicoGraphics(display=DISPLAY, pen_type=PEN_RGB332, rotate=0)

# Create a new JPEG decoder for our PicoGraphics
j = jpegdec.JPEG(display)

# Open the JPEG file
j.open_file("testfile.jpg")

# Decode the JPEG
j.decode(0, 0, jpegdec.JPEG_SCALE_FULL)

# Display the result
galactic.update(graphics)

# wait
while True:
    # if A, B, C, or D are pressed then reset
    if pressed() != None:
        machine.reset()
2

You seem to be setting up PicoGraphics twice there - try getting rid of this line:

display = PicoGraphics(display=DISPLAY, pen_type=PEN_RGB332, rotate=0)

and then change the jpegdec setup line to:

j = jpegdec.JPEG(graphics)

3

Yes, I had copied some code without noticing the double definition. The problem however doesn’t lie there.

I noticed that the issue is with “pen_type=PEN_RGB332”. If I use this when defining PicoGraphics, e.g. if I use : graphics = PicoGraphics(DISPLAY, pen_type=PEN_RGB332), nothing is displayed on the Unicorn’s screen.

If I omit the pen_type definition, I get an entirely blue screen (tried using different jpeg files).

The issue therefore seems to be with the decoding. I noticed that in the original library that has been ported to the Unicorn, the jpeg files are transcoded from jpeg to c arrays. Wondering if this is needed here also.

Has anyone managed to get the Unicorn display to show jpegs? If so, could you share your code?

4

Ahh yes; the Galactic Unicorn doesn’t play nicely with an RGB332 pen (which is also a problem with some of the sprite stuff) - I’ve got a PR to fix that sat in the queue (although I think the whole pico repo is in a bit of flux so I don’t know when it might get merged)

1 Like
5

This works for me, running v1.19.12 MicroPython. Might be worth upgrading to the most recent firmware if you’ve not already - I think there have been fixes to jpegdec in the last few versions.

from picographics import PicoGraphics, DISPLAY_GALACTIC_UNICORN as DISPLAY
from galactic import GalacticUnicorn
import jpegdec

galactic = GalacticUnicorn()
graphics = PicoGraphics(DISPLAY)

# Create a new JPEG decoder for our PicoGraphics
j = jpegdec.JPEG(graphics)

# Open the JPEG file
j.open_file("gradient_pink_blue.jpg")

# Decode the JPEG
j.decode(0, 0, jpegdec.JPEG_SCALE_FULL)

# Display the result
galactic.update(graphics)

PXL_20230131_110232279
PXL_20230131_1102322791920×870 143 KB

Here’s the image I used if you want to give it a try:
gradient_pink_blue

2 Likes
6

Thanks Hel, updating the MicroPython to its latest version was the solution. It now works fine. Great!

1 Like
7

Thanks for this example. When I tried this program with your image, I get the following error:

Traceback (most recent call last):
File “”, line 18, in
OSError: [Errno 2] ENOENT

Sorry if this an obvious error - I am new to this board. Any ideas - I am using the latest uf2 file for the galactic unicorn (v1.19.12).

Thanks

8

ENOENT means it can’t find the file - check the image filename and how it’s referenced in the code match? (look out for .jpg vs. .jpeg - I’ve been caught out by that before!)

9

Thanks! I was foolishly trying to run this from my computer. Loaded the files to the pico and works perfectly.

1 Like