Uploaded images are pixelated

I am using a GUI created by someone else and it's working great with the sample images I uploaded from their github, which are about 10MB .jpg files that are 3684 x 4912 x 3 in size. I am trying my own .jpg files which are 178KB and 688 x 917 x 3 in size, and they are all pixelated. Is there a way to remedy this without code? Is there a setting somewhere that will improve the image quality? Or do I need to start with a better quality image to begin with? These are images that I swiped from the web and a powerpoint file, so I am thinkng I just need better quality images.

Answer 1

[Star Strider]

JPEG images have problems because of the discrete cosine transform used to encode them. See the Wikipedia section on JPEG compression for details.

For best results, use PNG.

[Daniel]

Agreed, but also, you'll run into blockiness sooner on smaller images. OP's images are about 1/4 the size in each dimension of the reference images, so for equivalent compression ratios, they'll get blocky 4x as fast.

Either way, I think the answer is "yes, you probably just need better quality images with more pixels" (as long as the compression ratio on those images isn't ridiculous, which will also cause blockiness per Star Strider's answer).

[Julie]

I did try a PNG file, the same file that I had uploaded as JPG. The image was processed but had the same pixelated look as the JPG file. I agree with Daniel that more pixels will fix this problem. I've written to the author because they have trained the GUI on 12000 images so they should have an idea what the limitations are. If they ever respond.

Star, thank you so much for writing back right away! That's good to know about JPG vs PNG and I will keep it in mind when I'm using this program. The author used all JPG files as samples so I did the same, but ti's good to know that I can also use PNG and that it might even be better to use PNG. Just not for these low quality images that I have.

[Star Strider]

As always, my pleasure!

[Enrique]

Does someone know if it is possible to insert a vector image (.pdf or .svg) to solve the pixel problem?

I have tried with .svg but simulink converts it to a very pixelated image. :(

[Daniel]

@Enrique, since the original poster's question has been answered, you'll get a lot more traction with the community if you post your question in its own thread.

[Enrique]

@Daniel I have created a new thread: https://de.mathworks.com/matlabcentral/answers/1954094-insert-vector-image-or-vector-graphic-in-simulink

[Julie]

Yes I actually contacted the author of the GUI who changed the code so the GUI will upload TIFF images now, less lossy and more compatible with our slide imaging program. She agreed that the GUI was trained on larger images and the lack of information in the images will compromise the ability of the GUI to classify the images. Thank you everyone for your help.

[DGM]

If the GUI utilizes uiimage() components for image display, then you will likely see JPG artifacts regardless of the original image format. Using larger images will simply make them less visually conspicuous, but they'll still be there.

https://www.mathworks.com/matlabcentral/answers/727898-uiimage-introduces-artifacts-how-to-fix#answer_1477121

I don't have enough information here to be certain, but that's a quite plausible explanation.