Bitmap images (also known as raster images) are made up of pixels in a grid. Pixels are picture elements; tiny dots of individual color that make up what you see on your screen. Bitmap images are resolution dependent. Resolution refers to the number of pixels in an image and is usually stated a dpi (dots per inches) or ppi(pixels per inches). Bitmap images are displayed on your computer screen at screen resolution. Because bitmaps are resolution dependent, it’s difficult to increase or decrease their size without sacrificing a degree of image quality.
Advantages of bitmap image:
- Pixels ia a grid
- Resolution dependent
- Resizing reduces quality
- Easily converted
- Restricted to rectangle
- Minimal support for transparency
Popular file formats that are used for bitmap data:
- BMP: An outdated and limited file format that is not suitable for use in digital printing.
- GIF: Mainly used for internet graphics
- JPEG: Or rather the JFIF file format, which is mainly used for internet graphics
- PICT: file format that can contain both bitmap and vector data but that is mainly used on Macintosh computers and is not very suitable for digital printing.
- PSD: The native file format of Adobe Photoshop
- PNG: Mainly used for internet graphics
- TIFF: Popular and versatile bitmap file format
- PCX: Used in Paintbrush
Vector images are made up of many individual, scalable objects. These objects are defined by mathematical equations rather than pixels, so they always render at the highest quality. Objects may consist of lines, curves, and shapes with editable attributes such as color, fill, and outline. Changing the attributes of a vector object does not effect the object itself. You can freely change any number of object attributes without destroying the basic object Because they’re scalable, vector-based images are Resolution independent. You can increase and decrease the size of vector images to any degree and your lines will remain crisp and sharp, both on screen and in print. Fonts are a type of vector object.
Popular file formats that are used for vector data
Bitmap data can be saved in a wide variety of file formats. Oddly enough the most relevant formats for the printing industry are also capable of storing bitmap information:
- EPS: the most popular file format to exchange vector drawings even though PDF is quickly gaining ground.
- PDF: Versatile file format that can contain just about any type of data including complete pages.
- PSD: The native file format of Adobe Photoshop.
- AI: The native file format of Adobe Illustrator.
- CDR: The native file format of Corel Draw.
- GIMP(XCF Files) : Open sources “Photoshop work-alike” which is gaining in popularity and sophistication
Advantages of vector image:
- Resolution independent
- No background
- Inappropriate for photo-realistic images
- Metafiles contain both raster and vector
- Perfect for digital t-shirt printing