Paintbrush is a lite image edition tool very similar to Paint, the one we can find on any Microsoft Windows PC.
Paintbrush offers classic edition tools: pen, selector, line, curve, eraser, geometric shapes, text, fill,...
The user can select the canvas size where he'll draw the picture, although it include some ones by default: 640x480, 800x600, 1024x768.
The unit used is the pixel and you'll be able to export the files as JPEG, PNG, BMP and GIF.
In short, this is a lite and basic editor that can be useful for minor editions and it is really far from advanced image edition tools like Photoshop.
