TABLE 23.1 Picture Quality DefinitionsYou may have noticed that dots per inch (dpi) is not mentioned in the definitions in Table 23.1. This
is because dpi has nothing to do with the quality of a picture. dpi is actually an old term that has to do
with printing pictures on a computer printer.
By-the-Way: Horizontal and Megapixel
Often a camera’s ability to take still HD photos is rated by giving the height
(horizontal) only or giving a megapixel rating (multiplying the height by the width). For
example, an HD camera with a resolution of 1280×720 could be listed as 720 or 720p.
Its megapixel rating would be 0.92MP.If you do not know a picture’s resolution, you can determine whether the image is HD by using the
Image Viewer utility on Raspbian. In the Raspbian GUI on your Raspberry Pi, click on the LXDE
Programs Menu icon. (If you need help remembering where this icon is located, refer to Hour 2,
“Understanding the Raspbian Linux Distribution.”)
Within the LXDE menu, in the Accessories submenu is File Manager. When you open the File
Manager, you can navigate to any photo or image files currently stored on or accessible by your
Raspberry Pi. When the photo or image files are showing in the File Manager window, you can right-
click an image file and have the Image Viewer open it. Figure 23.1 shows an example of an image
file, /home/pi/python_games/cat.png.