Updated : 2021
Click the crop image (for the mosaic effect in Adobe Illustrator)
Set rectange for the crop
You can set the PPI to 300 or 2 or 1 etc (set to 1 for a mosaic effect)
Click apply
How to quickly create a mosaic effect in Adobe Illustrator can be achieved by using the crop image tool which was introduced into Illustrator. The mosaic effect can then be manipulated further by using the trace and other tools such as perhaps using the color adjust balance and the color guide tool to recolor the Illustrator mosaic design.
The key thing here is the PPI. You can create an interesting mosaic effect by using PPI to 1. OK, you could also create the mosaic effect in a raster application and then import the design into Illustrator (probably just as easy)
You can then use the image trace feature on the cropped image and use the color mode for the trace.
file menu
place image
click embed
resize image and make a lot smaller
crop image
set PPI to 1
click apply
You should now have a lot blockier image than if you were just going to use a 3000 x 3000 image (and set to 1).
Select the mosaic effect image
go to the edit menu
edit colors
adjust color balance
preview ON
set the red and green etc sliders
OK
You can also re-color the design using the adjust color balance tools (as well as other third party plugins etc). So if you want a red or yellow etc design, you can do this in Photoshop beforehand or just apply a color balance effect to the mosaic
Tricky but certain it can be done. I have found it fairly difficult to achieve with tools such as the image trace. You could, of course, use the eyedropper tool and then create your own squares using the displayed grid. It can be done. You can also just use squares and create an abstract design loosely based on the colors of the mosaic squares. You could fill them with gradients instead. Using the image trace probably can result in a good result but I have ended up with many different and unusual shaped squares during my tests on converting using the image trace. Another option would be to export the result and then use an online vector conversion tool or something like corelTrace (which also has a mosaic effect)
select mosaic image
click image trace
goto to the image trace panel
click ignore white
set noise to minimum
set corners to less
set paths to high
set mode to color
set palette to document library
set colors to all
object menu expand
object menu ungroup
Select cropped image (after PPI set to 1)
Click image trace
Go to image trace panel
Set mode to color
Set colors to all or document library etc
Change paths etc in the image trace panel such as setting paths very low
Expand
Ungroup
The image trace can be used with the 'mosaic' cropped image in Adobe Illustrator. You can use the color mode along with different colors and paths etc and then expand and ungroup and use the cropped paths as abstract designs. You can also use the result with the color guide to create interesting colorful artworks from the cropped images