Step 2 - Start Recording Comic Effect Action

Press Alt-F9 or choose Actions from the Windows Menu. Select New Action. Name it Comic Effect and choose a Set to place it under. Click Record to star saving your actions. A red record button will appear at the bottom of the Actions panel. You can press the double arrow at the top of the panel to collapse to an icon to get it out of the way. Note: if you save your work in the middle of recording, you get back to where you left off when you load back in the file.
Choose new action
Action Options Dialog

Step 5 -  Apply the Poster Edges Filter

Apply the Poster Edges filter with Edge Thickness 1, Edge Intensity 0, and Posterization 6. In Photoshop CC and above Poster Edges is found in the Filter Menu under Filter Gallery. In  earlier versions you can find it in the Filter Menu under Artistic.
After Poster Edges Filter Applied
Expand your actions panel (If you reduced it) then Select the black square button at the bottom to stop recording
In the Actions panel Click the little grey box to the left of the first levels action. This will allow the action to pause and allow you to modify the initial levels if you are not satisfied with the auto levels.

Step 8 -

Stop recording adjustment
Pause Action at first Levels adjustment

Colorful Poster/Comic Effect Tutorial Page 2

I started off with a cropped version of the original. The Effect on the full size image is  too detailed to be placed on an web page I either had to have a giant file size to slow down  the page significantly or a compressed filesize that would lose the detail of the effect. I  decided to compromise by cropping a smaller section of the picture. and using a fairly large  but not massive file size. You can work along with the original picture if you wish. I made a  full picture at 300 ppi and printed it and it came out great. The cropped image is 2920 wide  and 2257 high at 72 ppi.

Step 1 - Crop the Image

Seoul Street Cropped Original
Image Size Box

Step 4 -  Apply Gaussian Blur with Darken Blend

Next apply a Gaussian Blur Filter. We'll set the blur to 10 for now. (We can modify it later if necessary). The purpose of the blur is to even out and soften the colors and details.
Once the blur is applied. Right-Click on the Gaussin Blur words in the layer panel and choose Edit Smart Filter Blending Options.Alternatively you can double-click the double triangles with line above them to the right of the Gaussian Blur filter in the layer panel. When the blending dialog box appears, change the blend mode to Darken. The Darken Blend brings out lines and darker areas.
Image after Gaussian Blur Filter Applied
Gaussian Blend Dialog box
Comic Effect Page  1  2  3

Step 3 -  Open Image and make Auto Levels Adjustment

Open the image and double-click to unlock. Press Control L or choose adjustments>levels from the Image Menu. Select the auto button to give you a good starting point. Then click ok to accept. Right-Click on the layer and choose Convert to Smart Object.  From this point forward we will be using the smart object and  adjustment layers so settings can be changed easily after we're done.
Auto Levels Dialog Box

Step 6 -  Add a Levels  and Hue and Saturaion Adjustment Layers

Add a Hue and Saturation adjustment layer by clicking the new adjustment layer icon at the  bottom of the layers panel. Click the X in the upper right corner to close and leave at the  default settings for now.
Add a levels adjustment layer by clicking the new adjustment layer icon at the bottom of the layers panel. Select the Auto button for now. Click the X in the upper right corner to close.
Make levels adjustment
Make Hue-Saturation Adjustment
 

Step 7 -  Add a Saturation Layer

Create a new layer by clicking Layer>New Fill Layer>Solid Color.When the New layer dialog  box appears make the name Saturation, the mode Saturation and the opacity 10% click ok to  accept. When the Color picker appears choose a light blue color such as #70D0F0. Click OK to  accept.
Add Saturation Layer