What are raster images?

A raster image is simply an image made up of tiny pixels of color. Depending on the size of the image there will be hundreds, or even thousands of different pixels placed together in the right way to form the image you see.

In the following raster image, you can see that at normal size it looks great, and there is lots of different shading. However, the right-hand side shows that when you zoom into this image using Prezi, you will start to see the individual pixels that make up the shaded areas. This degrades the quality of the image when viewed at this size.

The preceding image has been saved as a PNG (Portable Network Graphics) file using the much loved Adobe Photoshop.

Some other raster graphics editors you could use to create raster images are:

• KolourPaint

• GIMP

• GrafX2

Note

All of the preceding raster graphics editors have their own advantages over one another, so I'd recommend you take 15 minutes out of your day to research them and see which one you would prefer.

Raster file formats

I mentioned that the example image shown previously was saved as a PNG file which is one of the formats Prezi will accept through the insert image menu option. You probably know already that Prezi will also accept JPEG (Joint Photographic Experts Group), GIF (Graphics Interchange Format), and, PDF (Portable Document Format) images, "but what do these different files mean?" I hear you shout!

Raster formats within Prezi
File format	Uses	Tips
.jpeg	Uses 16 million colors, so it is perfect for photographs and images with lots of shading.	Compression can be adjusted so you decide the trade-off between image size and quality.
.gif	Great at compressing images that have large blocks of the same color, that is, logos or shapes. Also supports transparency.	Avoid using this format for photographs and images with shading.
.png	Has many of the same qualities as .gif but compresses images in a much better way.	Supports transparency which is extremely useful in Prezi when overlaying images.
.pdf	This format preserves all visual elements within the file and compresses the file size very effectively. This format is useful when importing PowerPoint slides. This is discussed later in Chapter 7, Importing Slides into Prezi.	Prezi desktop player will need to convert the PDF files so an Internet connection is needed for this.