While digiKam can’t handle Adobe Photoshop curve presets directly, the application supports curves in the GIMP-compatible CRV format. So if you want to use Adobe Photoshop curve presets with digiKam, you have to convert them into .crv files — and the acv2gimp.py Python script can help you with that. Before you put the script to use, make sure that Python is installed on your system. Next, use the chmod +x acv2gimp.py command to make the script executable. Once you’ve done that, you can convert a curve preset by running the ./acv2gimp.py command followed by the name of the file in the ACV format:
By default, the converted file has the same name as the original preset sans the file extension (e.g., curvepreset.acv becomes curvepreset), but you can use the -o parameter to specify a different name:
./acv2gimp.py -o converteredcurvepreset.crv curvepreset.acv
To load the converted curve preset in digiKam, open a photo for editing and choose Colors → Curves Adjust. Press then the Load button and select the converted curve.
Although digiKam can’t rival dedicated image manipulation applications like the GIMP, it does have several essential editing tools which can help you to turn plain photos into striking images. For example, using the Curves Adjustment tool, you can apply the cross-processing effect to a photo. This effect is achieved by adjusting curves in three separate channels. In the Red and Green channels, you need to raise the red and green levels in the highlights, and to drop the red and green levels in the shadows. You have to do the exact opposite in the Blue channel.
In digiKam, open the photo you want to edit, and choose Color | Curves Adjustment. Select Red from the Channel drop-down list and use the mouse to adjust the curve. Repeat this procedure for the Green and Blue channels.
Instead of fiddling with curves, you can use a preset file created by yours truly as a starting point. Grab the preset file, press the Load button in the Adjust Curves window, and select the downloaded file. You can then tweak the existing settings to your liking. Once you’re satisfied with the result, save the modified profile by pressing the Save As button. So next time you want to apply the cross-processing effect, you simply load the saved preset file.
Do you have your own favorite presets? Feel free to share them with others.