delaboratory is an image postprocessing application. It allows you to modify the color and contrast of a photo in a creative way, using curves, a channel mixer, an equalizer, blur, an unsharp mask, high pass, vignette, dodge/burn, shadows/highlights, and blending in different colorspaces (sRGB, ProPhoto, LAB, CMYK, LCH, HSV, HSL) with floating-point precision. Each operation is stored as an adjustment layer, and you can watch a realtime preview.
