Have you ever tried enlarging images and then images became blurry? Is there a way to enlarge images without losing quality?
If the answer is Yes the images are Vector graphics while, if you answer No , then the images are Raster (Bitmap) graphics. First, take a look at the following example.
The Raster (Bitmap) image becomes blurry when enlarged, however the Vector image keeps the same resolution regardless of enlarging the size.
There are two types of images in the digital world - Raster (also called Bitmap) and Vector.
Raster (Bitmap) images are composed of pixels. Every shape is composed of thousands of pixels which is why we cannot see individual squares while looking at a bitmap image. Each pixel is a tiny square with assigned color value. They are created using a grid of pixels to define the image. When you attempt to increase the size of an image created in a raster based program, the pixels defining the image can be increased in either number or size. Increasing the number of pixels or making the pixels bigger in an image results in the original data being spread over a larger area. Spreading the pixels over a larger area causes the image to begin to lose detail and clarity.
Generally Raster images are created through the process of scanning source artwork or "painting" with a photo editing or paint program such as Corel PhotoPAINT or Adobe PhotoShop. Pictures taken from a camera are Raster images. Majorities of images on the Internet are Raster images as well.
Popular Raster file format extensions include: JPG/JPEG, GIF, PNG, BMP, TIFF, PSD (Adobe Photoshop) etc.
You will want to avoid using raster images in creating and working with logos and illustrations. In some instances a raster image can be used successfully when working with logos, especially if there the logo is more image rather than text based. It is recommended, though, to create the logo as a vector file and save copies as raster images as needed for specific projects.
Raster images are the preferred method when working with photographs. When photos are taken with a digital camera or copied on a scanner, the resulting files are raster images.
Almost all of the images you find on websites are raster images, even those that may have originally been created with paths. Raster images are typically acceptable for digital publication but may not work well in printed projects. Often these files are saved as low resolutions and are not suitable for print reproduction.
In printed mediums — such as books, magazines and newspapers — raster images are often used to reproduce photographs. Images are saved at a high DPI so that quality will not suffer during the printing process.
To printer correctly a raster image, printers require that you provide them with files at the correct size: the dimension you want to print your image at, and the pixel resolution for that particular project. The pixel resolution is the amount of pixels within each inch called ppi (pixels per inch).
How large a raster image can be printed - and maintain quality - depends on 2 things:
- The pixel dimension of the image (e.g. 6824 pixels wide by 2345 pixels high).
- The pixel resolution: pixels-per-inch (ppi), how many pixels per inch are required by the particular printer.
Different types of printing have different resolution requirements. On average:
- Paper printing require a minimum of 300 ppi.
- Shirt printers require a minimum of 240 ppi.
IMPORTANT: Once the image is created at a certain dimension, you may not be able to use this image at a larger size without losing quality. When you manually increase the resolution with a program like Photoshop, Photoshop randomly adds pixels and the result will most likely be a high resolution image of poor quality.
How to determine what size your raster image must be for printing:
Multiply the resolution required by the area to be printed. For example, iff a printer requires a minimum of 300 ppi and you want to print an image in an area that is 5 inches wide, multiply 300 (pixels/inches) x 5 inches = 1500. Your image must be at least 1500 pixels wide.
Vector images are made of lines and curves (or paths). They can be scaled up or down without any loss of quality. When an illustration (drawing) program sizes a vector image up or down, it simply multiplies the mathematical description of the object by a scaling factor. For example a 1″ square object would need to be multiplied by a factor of 2 in order to double in size.
The math is simply recalculated to produce an object twice the size of the original. Because vector images scale up or down without the loss of image quality, they can be output at any resolution both on screen and in print.
Generally Vector images are created through the process of drawing with vector illustration programs such as CorelDRAW, Adobe Illustrator, or PowerPoint.
Popular Vector file format extensions include: EPS, AI, CDR, PPT/PPTX, WMF/EMF, SVG, et al.
Vector images are the No. 1 option when designing or creating a logo or illustration. Because of the way images are created and saved, you will have more flexibility with making changes and be able to use your image at a variety of sizes. You may only need a web logo now, but image how great it would be to have that image ready to use on a banner or merchandise later without having to create it all over again?
Photographs are not vector graphics. Only illustrations that are made to look like photographs can be created in a vector workspace.
Most companies create all of their logos and insignia as vector images. These files are saved and are used as the basis for raster copies that get used in print and web publishing. Keeping a nice library of vector images can save you time because of the ability to resize on the fly.
High-resolution, high-quality clip art is often developed and sold as vector images as well. You will get more flexibility and more for your money when you buy vector-based clip art rather than high-DPI images.
Vector vs Raster
In short, Raster (Bitmap) images generally refer to photographs, pictures with great color detail, but can’t enlarge without becoming blurry, while Vector images generally refer to illustrations, drawings with ability to enlarge without losing quality.
Here are key points about vector images:
- Resolution independent
DPI vs PPI
DPI - Dots per Inch: This is the amount of ink dots the printer will put on each pixel of your image. The DPI is set by the actual printer device and it is not something in the image for the graphic designer to manipulate.
PPI - Pixels per Inch: Digital raster images are measured in pixels, or picture elements. How many pixels per inch is determined by the device you create the digital image with: camera, scanner, or graphics software and can be modified with a photo/paint editing software.