Raster ( or bitmap) graphics are a type of digital image composed of small squares called pixels arranged in a grid. The amount of pixels goes to define the resolution, generally stated as pixelWidth x pixelHeight (1920 x 1080), the greater the number of pixels the more detailed the image.

Unlike vector graphics where content is reproduced through mathematical equations, making it continuous and infinitely scalable, the raster image is discrete, limited by its resolution. By scaling a bitmap image beyond its original resolution we will lose in quality and definition.

Another key feature of raster graphics is color depth. Each pixel can contain a different amount of data(bits). Depending on the number of bits, each pixel can represent a different number of colors. The more bits we have the greater the color depth. For example, if we had a black-and-white image, thus with a single channel, at 1 bit we could reproduce only two colors, precisely black and white. The bit raprrepresents a binary state, either zero or one, and is the fundamental unit of digital.

Now let us take the same image as before, but this time it will have a color depth of 8 bits. In this case the reproducible colors will be 28 or more simply 256 ( only grays having a single channel). The same applies to a color image. To reproduce color visually we need three channels, red, green and blue . Supposing we have 8bit for each channel we will then have 256 x 256 x 256 that is about 16 million colors

As the depth of resolution and color depth increases, so does the weight of the image, a factor to consider especially when working with the Web. For this reason, it is essential to use file types suitable for the context in which the bitmap image is to be used. Common formats include JPEG, PNG, GIF, BMP, WebP and TIFF.