Q: What is the difference between vector graphics and bitmap graphics?
A: A vector graphic is defined in a mathematical nature which makes it resolution-independent. A vector graphic can be printed clearly at any size. A bitmap image is formed by a rectangular grid of small squares, known as pixels. Each pixel contains data that describes whether it is black, white, or a level of color. Bitmap graphics are resolution-dependent they can appear jagged and lose detail if they are created at a low resolution and then enlarged or printed at a higher resolution.
Q: Where do vector graphics come from?
A: Vector graphics are typically created by illustration software such as CorelDraw, Adobe Illustrator or Macromedia Freehand.
Q: Where do bitmap graphics come from?
A: Bitmap graphics are typically created by pixel-based image editing software such as Corel PhotoPaint, Adobe PhotoShop or Jasc PaintShop Pro. Additionally, bitmap graphics are generated from digital cameras and scanners.
Q: Can bitmap graphics be converted to vector graphics, and vice versa?
A: Yes, sort of and yes. Software such as CorelTrace or Adobe Streamline can convert bitmap images to vector images but the results may vary from horrible to wonderful depending on such diverse variables as source image quality and personal perception.
Vector images can be converted to bitmap images by opening them with Adobe PhotoShop or by rendering them (exporting) as bitmaps from vector-based image editing applications. Please note that converting a vector image to a bitmap image is rarely necessary, removes the resolution-independence of vector graphics, and should only be done if you have a very specific reason to convert the graphic.
Q: What are the different types of bitmap graphics?
A: A one-bit (monochrome) image refers to an image that is a solid color, with no shades of that color. A continuous tone image refers to photographic images, whether they are full color, black-and-white images with shades of gray (grayscale), or single-color images with shades of that color.
Q: What guidelines do you have for bitmap graphics resolution?
A: One-bit images require at least 600 pixels per inch (1200 is preferable. Full-color, grayscale and single-color continuous tone images continuous tone images require at least 300 pixels per inch.
Q: Can I resize bitmap graphics in a page layout application?
A: Remember that guidelines mentioned above are for bitmap images that are used at their actual (final) size. If the image is enlarged in a page layout application, the requirements enlarge by the same amount. For example, enlarging a full-color continuous tone image 225% in QuarkXPress would require a resolution of 675 pixels per inch (the original requirement of 300 pixels per inch multiplied by the enlargement of 225%). It is best to avoid performing scaling in a page layout application, as these programs have no ability to change the actual pixels in an image.
Q: Can I resize bitmap graphics in PhotoShop?
A: PhotoShop can increase the resolution of a low-resolution image, but increasing the resolution of an image scanned or created at a lower resolution only spreads the original pixel information across a greater number of pixels and rarely improves image quality.
Q: I’ve heard Encapsulated PostScript (EPS) mentioned in the context of both vector graphics and bitmap graphics. How can it be both?
A: EPS files act as a container for transferring graphic information. When an illustration software such as CorelDraw, Adobe Illustrator or Macromedia Freehand creates an EPS file, it will be an EPS file that contains vector graphic information as long as the original objects were also vector objects. If any of the source objects are bitmaps, then they remain bitmaps when exported to an EPS file. This means that you cannot import a bitmap image into a vector-based illustration application, then export the image as an EPS file, and expect the resultant EPS file to magically contain entirely vector-based graphics.
When a pixel-based image editing software such as Adobe PhotoShop creates an EPS file, it is a bitmap EPS.
Q: Can I copy a graphic and paste it into my document?
A: While copy-and-paste is supported by most software, you will have much more predictable results by creating a link to your graphic. The graphic then remains outside of your document and is referenced as needed. Please refer to your software’s documentation for full details about creating links to your graphics.
Q: What is a PDF file?
A: Documents in Adobe’s Portable Document Format (PDF) preserve the exact look and content of the originals, complete with fonts and graphics, and can be printed, distributed by e-mail, and shared and stored on network systems (including the internet) for others to use and view. When properly created, PDF files have proven to be an excellent method for generating quality printing.
Q: Where can I find my fonts?
A: On a Windows-based computer, fonts can be located in two different places. First, check Start Menu>Settings>Control Panels>Fonts. Additionally, you may have a folder names psfonts (typically on the C: drive). Fonts in this folder are PostScript fonts and require two separate files to accurately define a font’s appearance. The first file, found in the psfonts folder, ends with a .pfb extension. The second matching file is found in the psfonts>pfm folder and ends with a .pfm extension. The font name can be accurately determined by double-clicking the .pfb or .pfm file. On a Macintosh computer fonts are found in the System Folder>Fonts. If you use a font management utility on either platform, fonts are found in a location specified by the utility.
