There are two different types of images used by graphic design programs: raster images (sometimes called “bitmaps”) and vector-based images.
A raster image is made of thousands of little dots, or pixels. Creating or editing an image with dots allows you to provide for rich detail in an image. Because every dot can be a different color, you can allow for any kind of color change.
Raster images are wonderful for rendering rich, full-color images, like photographs; they do, however, have some drawbacks.
Photo Editors are Raster Based
- Raster images are file-heavy. All of the zeros and ones that are used to make up each pixel result in large files sizes. Your computer must keep track of the zeros and ones and must change each one when editing. This is memory-intensive and may cause slower editing.
- Rasters do not resize well. When you resize a raster image, the pixels just get larger, making the image appear distorted and chunky/grainy.
- Photo editors, like Adobe PhotoShop, use raster-based images to allow for precise editing and total freedom in image appearance.
Illustration Programs are Vector Based
Vector-based programs approach image creation in an entirely different manner. A vector-based program does not render images on a pixel-by-pixel basis.
In a raster-based image creation program, a square would be made of thousands of pixel dots, while in a vector-based program the same square would be made of only four dots, one on each corner. These “vector points,” basically allow your computer to play Connect the Dots. Each vector point has information in it telling your computer how to connect each point with straight or curved lines, and with what color to fill in the closed shape.
In the printed image, the vector points would be invisible. Because the computer only has to keep four points in its memory, it is much easier for the computer to edit vector-based images. This also means that file sizes are typically much smaller with vectors than rasters, depending on size and complexity.
If you resize a vector-based image, it loses no detail. The vector points spread out and the computer just redraws the image. You can easily color, or recolor, a vector-based image very easily using a drawing program. Vector images can also result in smoother lines because the lines are not lines based in blocks, but based in curves.
Vector images do have some drawbacks, however. They are generally filled with a solid color or a gradient but can’t display the lush color depth of a raster. They also work better with straight lines or sweeping curves. If you are creating imagery for use in web with vectors, you will have to export them into raster file formats and open them in a raster program to do further editing, resizing, or adjusting depending on how you created the original image. As you can see, the drawbacks of vector images are significantly less than those of rasters.
Drawing programs, like Adobe Illustrator, primarily use a vector-based drawing mode to allow for scalability and clean lines.
Write a response which answers the following questions:
- What is a vector image? What is a raster image? What is the difference?
- Why do you think raster images are more helpful to start with?
- What did you learn that you didn’t already know? Why is it important?
Your response must be at least 3 paragraphs.