I have a photo of my dog and I thought it would be fun for my kids to reproduce it in chalk on our drive way in large scale, then look at it from our up stairs window (and hopefully learn about colors etc on the way!). We have the standard sidewalk chalk colors of light blue, yellow, pink, white. I thought the best process for this would be on photoshop to pixelate it then change the Color index and get a recolorized pixelated picture which my kids could reproduce square by square on my drive. Unfortunately when I try this I lose so much of the detail of the initial image. I understand the image will look different but I thought it would retain most of the detail. Does anyone have any tips/a different process to follow? Thanks for all the help in advance! Ps I am clearly not an artist or graphic designer so apologies for my lack of knowledge
I think your project has a couple of problems.
The resolution needs to be really low
In order for this project to succeed you need to find a balance between having lots of pixels, so the image will be nicely detailed, and not having so many pixels that's it's an overwhelming task to draw them all manually.
Let's take an image of a dog and scale it down to for example 64×64 px.
It's just enough to have a little bit of details, but there are still 4096 pixels! I'm guessing it's a bit too much for kids to get through. How long does it take to identify and fill a single square? 5-20 seconds? So roughly 6-23 hours to complete the whole image.
32×32 px might be a better choice.
Many details are lost, but when you squint your eyes, you can still tell it's a dog. But there are still 1024 pixels. So roughly 1.5-6 hours of work. Still a lot, but more manageable.
Making pixel art is harder than you think
Let's try to simply convert such a low resolution image to Indexed Color with a palette like this (note the presence of a gray color to indicate a square of non-filled sidewalk):
The result is very poor:
The algorithm isn't capable of going creative with the available colors and struggle to find a way to use such pale colors.
A better result will come from first converting to Indexed Color without forcing a palette:
Afterwards you can apply the chalk colors by altering the palette (Image > Mode > Color Table):
It's still not exactly what I would call an acceptable result.
You could manipulate your image before scaling down and converting to Indexed Color for a better result or you could try some online image to pixel art generator,
The truth is though, that artwork with a limited palette in such a low resolution requires a lot of manual work.
A pixel artist could spend hours making an image like this. Manually placing each pixel. Using a combination of experience and trial-and-error to create the perfect illusion. It's definitely within reach for a hobbyist, but I don't really know of any one-click solution.
Another game to play
Another way of transferring an image which might be fun is to first somehow simplify the image to a line drawing and then divide the image into a grid:
You then draw the same grid on the ground and copy the image square by square. It could be colored of course.