Rubik's Cube Mosaic - Complex Request

[Lenish]

Hi there everyone! I am doing Rubik's Cube Mosaics of 720 cubes (24x30 cubes - 72x90px) - You can see one of them here on my channel:

I am asking you if you could teach me how can I make the quality of my portraits.

I am using an online mosaic creator for my mosaics with little effects like (contrast, brightness, vibrance, saturation etc.) in Photoshop before I load the photo onto that site. Today I personally asked the instagram guy, Giovanni, and he answered me telling me he is not using this site for his mosaics and that he cannot disclose how he is doing them, because he is under contract at the moment. And also he said it is a long process.

Take for example this photo of Bob Marley, could you somehow teach me how he did that high quality mosaic from this photo?

PS: If you try to do it with that site you will see that even with a lot of touches to the contrast, color, shadows etc. the quality of the mosaic will not be as high as that of Giovanni's portrait.

Here is a portrait (of a big romanian youtuber) I worked on for the last 2 days and after 40 versions of modifications to the original portrait, this is the best result I could achieve using the website.



Basically I need to reduce the image to only 5 colors (Green is not used in Rubik's Cube mosaics, because it doesn't look good) - Red, Blue, White, Yellow, Orange
I would be really grateful if someone could figure it out, I am doing personalities from my country Romania, so it wouldn't affect Giovanni's work. I also tried GIMP to create mosaics, but with no success.

 

[colleague]

Hi

I would use the folowing method

1- bring more detail in the image (with free nik filter )
2- make the image 72 pixels x 90 pixels
3 - turn into black&white with adjustment laye
4- use posterize adjustment layer to become only 6 colors
5 - use gradiënt with only 6 colors of the cube

then you can use the sliders in the black&white adjustment to become the best result

here is PSD with the gradiënt that I made

 

[Lenish]

Thank you very much for the detailed explanation, it's amazing what you did! :O

But I tried to reduce the colors to 5 in posterize and also change the colors between them (while with yellow) and it doesn't work like intended. There are also some in between colors, not just the exact 5 colors that I want. Could you help me please with this problem?

 

[Lenish]

I managed to get a grip how to change the colors and not having those nuances of yellow anymore! Thank you so much for you help, it really is amazing what you did there! I really appreciate it!