automatic rgb to cmyk conversion

With this technique you can get as close as possible to getting cmyk images that look like their original RGB without overflow of black ink by changing the red channel into the cyan channel, the green channel into the magenta channel, and the blue channel into the yellow channel using multi channeling. Moreover you will do this in a script so that you can open and change multiple images very quickly.
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Automatic rgb to cmyk conversion



---The rgb Color mode is set up as per the requirement of the print house. And you made adjustments to the rgb image for corrections.

---Now open one image and lets set up the action script.

---Once the image is open go to the window menu and click on action.

Then on the action flyout panel create new-set by clicking on the create-new-set button, give it a name, call it "cmyking"

then you will create an action within this set by clicking on the create-new action button you will find next to the create-new-set button.

---Then give the action a name, call it action1. ( you can change it later)

---after you hit record (also a button next to the create-new-action button), all subsequent events will be recorded till you stop recording.

---now lets start recording the actions,

---Go to your image and duplicate it by going to the image menu and clicking on duplicate.

---Then name the duplicate cmyk.

---Now change the mode of the image from rgb to cmyk by going to the image menu again and then mode then cmyk.

---It will ask you to flatten the image, click ok.

---Then go to the channels flyout panel and only select the black channel. Then press ctrl A to select all the contents of that channel and press ctrl c to copy. Then close the cmyk image.

---Go back to your original RGB image and duplicate it again by going to image menu then duplicate

---Name this image multi.

---Now go to image menu then mode then click multichannel.

---It will ask you to flatten the image, click ok.

---Then go to the channels flyout panel and add a new channel. (go to the create-new-channel button on the bottom of the panel)

---Alt backspace to make the channel white.

---Then ctrl v to past the black channel you copied from your cmyk image.

---Then go ahead to the image menu then mode then cmyk.

---Then go to the layers fly out panel and click on the layer.

---Then add a hue and saturation adjustment layer.

---Push the saturation all the way to 100 percent. You will lower it down after the automatic process is complete to match the context of the image.

---Now we have to control for overflow of black and avoid shadow by smearing of ink beyond the absorption capacity of the paper. To do this go to the channels flyout panel.

---Go to the black channel. Duplicate it.

---Then invert the duplicate black channel by hitting ctrl i.

---Rename the inverted channel by double clicking on the name, call it shadow fixer.

---Then press ctrl and click on the thumbnail of shadow fixer. This will select all the spots of the image that would be smearing ink when printed.

---Now go to the layers flyout panel and insert the selective colors adjustment layer.

---on that panel, go to the black color from the menu,

---then go to the cyan and magenta sliders and lower both to -33, then go to the yellow slider and lower it to -25.

---then go to the action fly out panel and click on stop. now you are done recording your actions,

---now you have to tell photoshop to use the actions whenever you like.

---Go to file, automate, then batch. In the batch dialogue box select Set to CMYKing
---Action to action 1
---Source to folder,
---Click on the choose button and select the folder that has all the rgb images,
---Go to destination and choose folder,
---Then click on the choose button and select an empty folder you have already prepared to put the converted cmyk files in.
---then click ok and you are done

---you will see photoshop open and insert the actions you have specified. you will need to reduce the saturation of the hue and saturation adjustment layer according to the context of the image your self later on.

---you can save the action on another computer, click the SET you created on the action fly out panel (cmyking) and go to fly out menu and click save,