Image editing tools

Image Optimizer is a free and open source simple program for compressing images without loss of quality using JpegOptim and OptiPNG

Pixelitor is a free and open source, multi-platform advanced image editor with support for layers, filters, cropping and other functions

ImEditor is a free and open source, simple and versatile image editing program

Photoflare – free and open source, fast and simple, but powerful cross-platform image editor

LazPaint – free and open source, cross-platform light editor of images with multiple tools and filters

LightZone – free and open source, multiplatform digital darkroom software and professional-level photo editor

RawTherapee is a free and open source, cross-platform raw image processing program

XnConvert is a fast, powerful and free cross-platform batch image converter, It allows to automate editing for your photos