First, ensure that your images originally have good quality.
Bitmap images, such as JPG/JPEG and PNG, have a fixed number of pixels, so by scaling they may become blurry or pixelated. You may notice this in the images in this book as the production process required bitmap images instead of the original LaTeX output in PDF format.
Vector images, in contrast, are scalable without loss of quality. You can zoom in and out and they keep looking fine. An example of this is the Scalable Vector Graphics (SVG) format. It's not natively supported by LaTeX, but it can be converted to PDF or to TikZ (PGF). We will talk about TikZ and PGF in Chapter 9, Creating Graphics. Portable Document Format (PDF) and PostScript (PS) are vector formats, although they are allowed to contain bitmap images. Vector formats should be preferred over bitmap formats.
Today, pdfLaTeX is most widely used. It allows the inclusion of PDF images. Furthermore, the bitmap formats, JPG/JPEG, and...