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Merged
merged 1 commit into from
Sep 9, 2025
Merged

Flip byteorder #41

merged 1 commit into from
Sep 9, 2025

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relic-se
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@relic-se relic-se commented Sep 8, 2025

When working with framebufferio.FramebufferDisplay sources, the byte order of 16-bit pixel data was flipped, causing major color errors. This update simply changes the byteorder.

This fix has been tested on the Adafruit Fruit Jam using the following code:

import displayio
import supervisor
from terminalio import FONT
import vectorio

from adafruit_bitmapsaver import save_pixels
from adafruit_display_text.label import Label
from adafruit_fruitjam.peripherals import request_display_config

BAR_COLORS = (
    0x000000,
    0x444444,
    0x888888,
    0xcccccc,
    0xffffff
)
CIRCLE_COLOR = 0xff0000
TEXT_COLOR = 0xffffff

# initialize display
request_display_config(320, 240)
display = supervisor.runtime.display
display.auto_refresh = False

# create root group
group = displayio.Group()
display.root_group = group

# draw bars
for i, color in enumerate(BAR_COLORS):
    palette = displayio.Palette(1)
    palette[0] = color
    group.append(vectorio.Rectangle(
        pixel_shader=palette,
        width=display.width//len(BAR_COLORS),
        height=display.height,
        x=display.width//len(BAR_COLORS)*i,
    ))

# draw circle
palette = displayio.Palette(1)
palette[0] = CIRCLE_COLOR
group.append(vectorio.Circle(
    pixel_shader=palette, radius=min(display.width, display.height)//4,
    x=display.width//2, y=display.height//2,
))

# draw text
group.append(Label(
    font=FONT, text="Hello, World!",
    anchor_point=(.5, .5),
    anchored_position=(display.width//2, display.height//2),
))

# update display
display.refresh()

print("Taking Screenshot... ")
save_pixels("/sd/screenshot.bmp", display)
print("Screenshot Saved")

Before:
screenshot-before.bmp

After:
screenshot-after.bmp

Note: This update has not been tested on other display sources. It is possible that the source needs to be tested in some manner to decide the byte order.

Fixes #36

@FoamyGuy
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FoamyGuy commented Sep 9, 2025

I suspect that changing the hard-coded order like this is going to make it have a similar issue with BusDisplay or other types of displays. I'll test on a pyportal to try to confirm. If that is the case we may need to add a parameter or something that allows it to be set to the order required for a given display. Or maybe if display types are always consistent accross the same types it could just check the type of the display object and then behave accordingly.

@relic-se
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relic-se commented Sep 9, 2025

I suspect that changing the hard-coded order like this is going to make it have a similar issue with BusDisplay or other types of displays.

You are likely correct here. I don't have enough knowledge of how CircuitPython handles different types of displays to comment further.

If that is the case we may need to add a parameter or something that allows it to be set to the order required for a given display. Or maybe if display types are always consistent across the same types it could just check the type of the display object and then behave accordingly.

Adding an argument to handle this should be sufficient for now unless someone who has more knowledge in this area can comment further.

The only display types I am aware of which incur this issue are the following:

  • picodvi.Framebuffer
  • dotclockframebuffer.DotClockFramebuffer (mentioned in the associated issue, though untested with the fix)

tannewt
tannewt approved these changes Sep 9, 2025
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I think it is always this way because we match uint16_t on little endian machines.

https://github.com/adafruit/circuitpython/blob/a96f1123d92bd6b7638810429c4ef467147820c3/shared-module/displayio/TileGrid.c#L576-L581

@tannewt tannewt merged commit 2b972cd into adafruit:main Sep 9, 2025
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@relic-se
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relic-se commented Sep 9, 2025

Awesome. Thank you for the technical input, @tannewt! 🎉

@relic-se relic-se deleted the display-byteorder branch September 9, 2025 18:11
adafruit-adabot pushed a commit to adafruit/Adafruit_CircuitPython_Bundle that referenced this pull request Sep 12, 2025
Automated update by Adabot (adafruit/adabot@ba69525)
5a912ad 
Updating https://github.com/adafruit/Adafruit_CircuitPython_LTR329_LTR303 to 3.0.11 from 3.0.10:
  > Merge pull request adafruit/Adafruit_CircuitPython_LTR329_LTR303#12 from anujdeshpande/patch-1

Updating https://github.com/adafruit/Adafruit_CircuitPython_BitmapSaver to 1.3.8 from 1.3.7:
  > Merge pull request adafruit/Adafruit_CircuitPython_BitmapSaver#41 from relic-se/display-byteorder
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Issue with Sunton dotclockframebuffer display and bitmapsaver
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@relic-se @FoamyGuy @tannewt