Photo Curves
Photo editing app with focus on color grading using RGB and HSL curves.
The following tools are currently supported:

- RGB curves
- Hue to Saturation curve
- Hue to Hue curve
- Hue to Luma (Lightness) curve
- Luma to Saturation curve
- Luma to Hue curve
- Saturation to Saturation curve

Instructions:

With RGB curves - change brightness, contrast, control shadows, midtones, and highlights. Adjust white balance or make your picture a bit warm, cold, with a tint of yellow or may be blue.

With Hue to Saturation - make one color more vibrant than others, or leave one or two colors only, leaving the rest of the picture black and white. It looks cool!

With Hue to Hue - replace one color with another. You can replace multiple colors as well. This also allows you to create famous cinematic look a.k.a. "orange teal" color grading effect.

With Hue to Luma - adjust brightness of a specific color.

With Luma to Saturation - adjust saturation of shades, midtones, and highlights.

With Luma to Hue - change colors of shades, midtones or highlights.

With Saturation to Saturation - increase saturation of low saturated parts of a photo or decrease over-saturated parts to create evenly saturated HDR like pictures.