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About CAD

CAD (computer-aided design) software is used by architects, engineers, drafters, artists, and others to create precision drawings or technical illustrations. CAD software can be used to create two-dimensional (2-D) drawings or three-dimensional (3-D) models.

Difference between Raster and Vector image.

A Raster image is made up of individual pixels. Each pixel contains only one colour and is arranged in a certain fashion to make up the image. This is how normal pictures are displayed. The problem with raster image is that the maximum resolution is limited by the number of pixels.

That means, when you try and scale the image into a larger size, the quality drops and the edges of lines become fuzzy (staircase effect). This is the major limitation of using raster images.

A vector image is composed of paths, which are represented by mathematical functions. These mathematical function represents the actual borders and the different elements in the image. Hence the maximum resolution of the image is not limited by the number of pixels. These mathematical functions can scale easily giving lossless ability to zoom to any extent on the image.

You can erase pixels in a raster image using the eraser tool but, that is not possible in a vector image. In a vector image you can only trim the path according to some constrains

GIMP

Gimp is a free and open source raster graphics editor used for editing and retouching images. It is like a light weight version of Adobe Photoshop. Gimp excels in usability and functionality, it goes beyond simple image editing and gives you the ability to use layers to organize your artwork. There are many common tools in all the raster graphics editors.

Krita

Krita is a raster graphics software. It has a lot of customizable features. It is difficult to get your head around the multitude of tools and setting offered by krita. There are a lot of keyboard shortcuts which can ease the flow of work for the user.

Inkscape

I really like this software. The user interface is very intuitive and everything is customizable. Inkscape is used to create vector graphics. Its an open source platform, and you can save your files in an SVG format (Scalable vector Graphics). Which can by viewed in your browser.