Bitmap images and vector images

Differences between bitmap, raster and vector images

Bitmapped Images

Bitmap images (also known as bitmaps or raster images) are made of pixels on a grid. Pixels are small little squares or tiny dots of individual color that make up what you see on your screen. All these tiny dots of color come together to form the graphic images you see.

Resolution (dpi ppi) of bitmaps

Resolution refers to the number of pixels in a bitmapped image. Resolution is stated as dpi (dots per inch) or ppi (pixels per inch). Because the resolution of a bitmap is dependent on the dpi or ppi, resolution is difficult to increase without sacrificing image quality. When we reduce the size of a bitmap image through your software's resample or resize command, we essentially throw away pixels. When we increase the size of a bitmap image through our software's resample or resize command, the software must create new pixels. When creating pixels, the software must estimate the color values of the new pixels based on the surrounding pixels. This process is called interpolation.

Scaling a bitmapped Image

Scaling is when we resize an image by zooming in or zooming out, and this scaling does not effect the image permanently; it does not change the number of pixels (dpi or ppi) in the image. Scaling to a larger size (zoom in) in your page layout software causes a definite jagged appearance and will be very apparent in the printed image. Scaling a bitmap image to a smaller size (zoom out) has little effect and you are effectively enabling a printer to produce a cleaner print.

Cameras and Scanners

Scanners and digital cameras produce bitmaps.

Transparency

Bitmaps do not inherently support transparency but two specific bitmap formats, namely GIF and PNG, support transparency. A common misconception is that the transparent areas in a bitmapped image will remain transparent when it is saved to another format or copied and pasted into another application... this does not work well.

Vector Images

Vector images are made of many individual scalable mathematical objects rather than pixels. Vectors are always render at the highest quality. The mathematical 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 so that you may increase or decrease the size of vector image and your image remains crisp and sharp, both on screen and in print. Fonts are a type of vector object.

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