- Open an image
- Create a new file in another tab: File>New. Set Preset to the name of the previous image file.
- In this blank image, choose and paint in the required gradient in black and white monotone.
- Go back to the previous image (click on the tab)
- Select Image>Calculations.Set Source 1 as the original image, and Source 2 as the gradient image. Set Blending mode to Difference, and Opacity to 100%. The result can be set to New Document or as required.
- To make the image save-able, set Image>Mode to Grayscale, and then repeat and set Image>Mode to RGB colour. The image is now save-able in the correct colour space.
Wednesday, July 1, 2015
Notes to myself: Using Image>Calculations with Gradient mask
It is possible to create a selective positive/negative image using gradient mask. The resultant image is in B&W with parts of it in positive and part of it in negative.