PHOTOSHOP
Photoshop is a raster graphics software. It is used for raster graphics editing as well as creating digital art. In Photoshop we can crop, compose and edit images with help of its multiple layers feature. There are many colour models including RGB, CMYK, CIELAB, Spot Color and Duotone. In Photoshop it creates its own file formats : PSD and PSB file formats to support these features. The software also has ability to edit and render text as well as vector graphics.
In Photoshop we can create architectural presentation drawing as well as renderings for Plan, Elevation and Sections along with limited scope of rendering Exterior & Interior views.
You can purchase Photoshop Student version or Professional version online.
GIMP
GIMP (GNU Image Manipulation Program) is raster image and graphics software. It is used for drawing, free form ideation, image compositing/editing and for visual presentations. GIMP can still be a very useful and handy tool for quick image modifications.
GIMP is freeware and easily available online.