This might not be an RES specific question but I thought I'd give it a try since I didn't notice an option in normal reddit options *What's... More on old.reddit.com

Edit: See my reply to this comment. In most cases, this isn't really going to be possible by simple means. When you download a JPG (for example), it only knows the pixels that it, well, has. Say you take a picture with your phone camera. Your phone camera can only see so much detail, each "unit" of detail being a solid block of color, a pixel. To increase the quality & resolution of that image would mean adding pixels to the image the camera hadn't originally seen. Photopea's default photo expansion option is "Bilinear"; this takes the color of a pixel ("Pixel A") & the color of a pixel next to it ("Pixel B"), finds the average color of the two pixels, & places a pixel of that average color between Pixel A & Pixel B (then does the same in every direction with every single pixel you increase in the photo). Another expansion option is "Nearest Neighbor": if you use this, it takes the pixels it has & "expands" (duplicates) them, essentially just making the pixels larger & therefore resulting in rigid "pixilation." This is useful if you're editing something with straight, sharp edges, like a bunch of rectangles. Photopea's third option is "Bicubic Sharper," but I wouldn't really recommend using that for expanding an image's size, only maybe reducing it. The sharpening aspect would just result in more degradation of quality. However, you can scale vector graphic file types (such as SVG files) infinitely, as those use math/geometry on a Cartesian plane. Now, if you are really sure you can't simply find a higher resolution copy of your photo, there are some softwares with AI able to make an attempt at guessing what pixels go where. I don't have any recommendations, as it's not something I've looked into much, but you can try searching "increase image resolution AI online" or something of that sort and hope to find something free, or perhaps with a free trial. More on reddit.com

Try waifu2x. It's made to upscale anime images (e.g. lines and flat color), so it might work well with your image.

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Looking at the images, I do not agree that they necessarily need to be vectorized.

First thing to try: In Photoshop, use Image/Image Size, check Resample, and use the Preserve Details 2.0 resample method

Second thing to try is run it through the trial version of AI Gigapixel, which uses machine learning-based detail enhancement.

Because of the mix of text and graphics, and the fact that it's hand-drawn line art with lots of fine intersections and broad gray background transitions, I think vectorizing them could be time-consuming and difficult to get right. Running autotrace is easy, you just push a button, but I really doubt what comes out the first time is going to look the way you want. You'll spend another few hours tweaking the settings, waiting for it to complete another run, and repeating those steps until it looks right.

This is for a PC case, not an art gallery. People are not going to be sticking their noses up against it looking for pixels. I think upscaling might work out fine.

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