Edit an image's data so that a digital camera can read it

Question

Context

I have a Polaroid PoGo Zink printer (link to manual) that I would like to print an image on. Unfortunately I cannot get the Bluetooth to connect succesfully to any of my devices, so I am trying the following workaround to print over USB:

1. Get one of my digital cameras:
   • Canon IXUS 115 HS
   • Nikon S1
   • Panasonic DMC-LX7
2. Copy the image I want to print to the camera
3. Connect the camera to the printer over USB (using the supplied micro-USB cable) and print the image using PictBridge.

However, I am stuck on step 2 as any image I copy to the camera's SD card (e.g. this image) is shown as an "Incompatible JPEG":

Images that are taken with the camera, like this one, obviously display without any issue on the camera's display. I have tried in vain to understand what the differences are between JPG files that display in the camera and ones that don't.

The only "trick" that has worked was to open a camera image in Graphic Converter, rotate/resize/paste the desired image inside of the camera one and save with these settings, piggybacking on the camera photo's EXIF and file size/name. It has worked on and off, meaning something about this process is inconsistent.

Question

What should I do to my JPEG images such that they can be displayed on my digital camera after I copied them to the SD card, ultimately allowing me to print them on the Polaroid printer?

Tried so far

First off, here are the things I tried to connect over Bluetooth. All efforts failed, that's why am looking for the USB option now:

• On an iPhone:
  • the Polaroid app informs the user that the printer isn't connected;
  • user goes in the Bluetooth Settings window and tries to restart/pair/long press the printer's button, to no avail.
• On a 2013 iMac:
  • printer does show up in Bluetooth settings;
  • connection request and passcode steps work;
  • computer prompts to setup the printer after connection;
  • but it is impossible to add the printer to the printers and scanners preferences;
  • double clicking on the printer's name, a Bluetooth File Exchange's file browsing window appears;
  • selecting a file seems to send it to the printer;
  • but an unknow error -21860 is shown.
• On a 2020 MacBook Pro:
  • all the same as on the 2013 iMac;
  • but clicking the printer in the Bluetooth settings doesn't open Bluetooth File Exchange;
  • trying to print from Preview doesn't allow to browse or add Bluetooth printers even if they are detected in the Bluetooth Settings panel.

Here is a list of things I have tried to make images readable (and printable) by the camera - all have failed:

• renaming the JPG file to match the camera's default naming convention;
• resizing it to make sure the pixel count is even in H and W;
• copying EXIF data back and forth between images that work and images that don't;
  • This included EXIF preview (200x200) and DCF compatible preview.
• reducing file size to be around the same (approx 400/800Kb);
• re-exporting as a JPG in different image softwares;
• changing DPI;
• displaying invisible files in the memory card to see if there is a hidden preview file;
• editing JFIF data;

The only literature I have found online about a similar issue is here and here and it is very inconclusive and outdated.

Answer 1

jpeg is a container format like tiff, and the mpeg formats so there are various options which probably aren't implemented in your camera firmware.

JFIF & EXIF metadata types are incompatible with each other - a file can have one or the other.

Image encoding methods have evolved so the jpeg "standard" as used by old codecs and devices may lack features used in newer software. Progressive encoding was a later addition to enhance web use for example.

I did a bit of sleuthing with exiftool on the images you supplied and these are what I'm seeing as the most relevant information from the camera output.

Exif Byte Order                 : Little-endian (Intel, II)
...
Compression                     : JPEG (old-style)
...
Image Width                     : 1600
Image Height                    : 1064
Encoding Process                : Baseline DCT, 
Huffman coding
Bits Per Sample                 : 8
Color Components                : 3
Y Cb Cr Sub Sampling            : YCbCr4:2:2 (2 1)

In your failing file...

Exif Byte Order                 : Big-endian (Motorola, MM)
Image Width                     : 633
Image Height                    : 525
Y Cb Cr Sub Sampling            : YCbCr4:2:0 (2 2)

The first of these will be pretty good at tripping up a decoder that is probably only built to decode files it created, and image height/widths that aren't a multiple of 8 can be a known issue for older devices.

ImageMagick is probably the tool you need here - it's a command line tool where you can be quite detailed in how you want the file to be encoded, you'll need to look through the docs to set the right options. Or you can get exiftool and play around with all the encoding options in your software until you get it matched up.

Answer 2

To start of: your actual question seems to be about printing an image on a Polaroid Pogo printer. Getting an image shown on the camera was just a workaround because you could not get the Bluetooth working.

Later on you found the steps to connect the printer over Bluetooth to your iMac (following roughly these steps, but got stuck in the file transfer.
The key is to ensure that the filename (that's the part without the file extension) of the file you want to print over Bluetooth does not contain a special character, i.e. only consists of letters and numbers.

E.g., instead of sending a file deja-vu.png try renaming it to dejavu.png.