ResizePixel - Free image editor to crop, resize, flip, rotate and convert images online
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
Bulk Resize Photos - Resize large photos in bulk
Krita - Krita is a professional FREE and open source painting program. It is made by artists that want to seaffordable art tools for everyone. Concept art. texture and matte painters, illustrations and comics.
PQINA Photo Editor - A free, fast, mobile-friendly, online photo editor to quickly edit pictures.
GIMP - GIMP is a multiplatform photo manipulation tool.