How do I replace the blue color with red in this image?

Question

I'd like to replace the blue in the linked image with red. What is the easiest and best-looking way to do this? I had the idea of selecting the gold trim and colorizing the inverse, but that would take way too long to trace all that gold.

I can take suggestions for Paint.NET, GIMP, or Paint Shop Pro 9.

Image can be found here: https://www.gettyimages.in/detail/illustration/antique-book-cover-royalty-free-illustration/180820456

Answer 1

I agree with the OP's opinion that selecting the gold trim is an interesting solution. We want to take the blue components in the original image and turn them red without changing the blue components in the trim.

Here is an approach that uses GIMP's layer masks and color channel extraction to separate the gold trim from the rest of the image so we can process the non-trim parts independently. Maybe it's more than you need, but my curiosity got the better of me. Since I went through the process already, might as well share!

I noticed the green channel in the original image could serve as a decent mask for the trim so let's start by extracting it:

• Create a copy of the original image on a new layer. Name this layer "TRIM MASK".
• Use Colors/Components/Extract Component on this new layer to extract the "RGB Red" channel.
• Select this entire layer and copy it to the clipboard
• Hide this layer, we are only using it to create a mask.

Now we have a decent mask to separate our image. Let's create a layer of gold trim.

• Create a copy of the original image on a new layer. Call this layer "GOLD TRIM".
• Right click on this layer and select "Add layer mask". Initialize to black (we will change the layer masks in the next step).
• Select the layer mask (the black rectangle next to the layer's preview), paste the red channel we copied earlier, and anchor it
• Hide the original image

Now, we have a layer that is relatively opaque where the gold trim is, and transparent elsewhere.

You can then add a layer of a flat color underneath. Call this layer "BACKGROUND".

The flat color looks a bit artificial, so let's bring some of the original texture back in by extracting it from the original:

• Create a copy of the original image on a new layer between the flat color and the gold trim layers. Call this "TEXTURE 1"
• Use Colors/Components/Extract Component on this new layer to extract the "RGB Blue" channel.
• Set the channel blending to Grain Extract
• Play with the layer Opacity until you get a satisfying result.

Finally, for fun, I stumbled on this result that I really like by adding the following layer:

• Duplicate the "GOLD TRIM" layer and place the duplicate just underneath it. Name this duplicate "TEXTURE 2"
• Use Colors/Components/Extract Component on this new layer to extract the "RGB Blue" channel.
• Select the layer mask and invert it using Colors/Invert
• Set the layer's blending mode to Multiply.

I hope this helps!

Answer 2

GIMP's Rotate Colors

I think Rotate Colors is a good tool for this job. Open the image in GIMP and choose Colors -> Map -> Rotate Colors...

Then choose a blue slice in "From". I chose 184.8° to 273.1°. Then choose a red slice in "To". I chose 327.2° to 47.4°.

Answer 3

Disclaimer: I'm a Photoshop user, and I know you're not asking for a solution in that software. I do suspect that apps like GIMP have very similar options with similar results.

Put a completely red layer on top of your image layer. (I used a red that was somewhat lighter and a lot more vivid than the eventual effect I'd like to achieve.) Then change that layer's blending mode to Screen or Lighten. Play around with the exact opacity to tweak the effect to your liking.

Answer 4

I don't use those tools, but I know how we can try it on Photoshop. You might find similar options in those tools you use. One way of doing this is adjust hue saturation. Add a Hue Saturation adjustment layer for this photo, and adjust values for Blue and Cyan.

You should get a required result. It might affect the gold color a bit but I guess it won't matter much. And if you have a high resolution image, it can work even better.

You can alter the values according to the type of red color you need.

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Method 2: I just figured it out how we can use another approach using GIMP.

There's Gradient Map feature in GIMP. You can create a custom gradient in gradients window and then apply gradient map using Colors > Map > Gradient Map which can give interesting result. Just make sure you pick brightest colors (which you don't want to change) almost similar to the original image's brightest colors.

Result after using this gradient for gradient map: