UPDATE:
I was wrong the direct upload does not work either. It just seems to because the image appears and I can manipulate it and then it just disappears.
Doing some spelunking in the docs suggests that LC has a 5MB upload limit. Given that my image is 5.9MB I see why it would be disallowed. There is still a bug worth fixing here IMO because it would be easy to just produce an error message that explains that rather than just fail unhelpfully.
I still have a problem. Even though I convert the image to a <5MB JPEG which loads up fine LucidChart randomly degrades the quality so that it is entirely pixellated. The end result is horrible. I am trying to import a high-fidelity image so that I can build a diagram where I point things out with callouts but if the viewer cannot see the detail in the image the callout is useless. Is there any way to tell LucidChart I need the full resolution image?
I can't understand this design decision.
ORIGINAL JPEG
AS DISPLAYED IN LUCIDCHART

Hi @matt t101 thank you for posting in the community! Just to make sure that we are on the same page please review our Work with shapes in Lucidchart and our Shape Libraries article from the Lucidchart Help Center and let me know if you have any questions about the set up or intended functionality.
Problems with uploading could be related to the size of your image. Would you mind resizing your image and trying again? -- we have a size limit of 4000 pixels.
I recommend resizing or compressing the image in order for it to upload. A quick workaround is taking a screenshot of the image and uploading the screenshot.
Please let me know if this is not the issue or if you continue to run into trouble uploading images.
It’s a shame that there is this 4000 pixels size limit. For UX design work, we typically like to copy-paste full page screenshots, which for can be very very long from the top to the bottom of a web page / app screen. The only alternative I’vefound right now is to copy paste and collate multiple screenshotsofthe same page to get to a decent quality…
You should definitely review that limit.
It’s a shame that there is this 4000 pixels size limit. For UX design work, we typically like to copy-paste full page screenshots, which for can be very very long from the top to the bottom of a web page / app screen. The only alternative I’vefound right now is to copy paste and collate multiple screenshotsofthe same page to get to a decent quality…
You should definitely review that limit.
Hi @foucauld, thank you for continuing this post and sharing your workaround. Unfortunately, there is currently a 4000 pixel limit, but we’re very interested in your feedback and committed to continually improving our products. Please first search the Product Feedback section of this community (with the filter Topic Type = Idea) to see if it’s already been submitted. If so, please add any additional details you’d like and upvote the request - this consolidation helps to refine feedback and properly capture the popularity of the request.
If no one has submitted this idea yet, please create one of your own and be sure to include details about your use case or what you’d like to see in this experience. This will also allow other users with similar requests to discover and upvote it, then add details of their own.
Finally, for more information on how Lucid manages feedback via this community, take a look at this post:
Thank you for sharing your feedback in the community. Please let us know if you have any questions!