Graphics formats and resolution

Image data is stored in a variety of different ways. Most common file formats consist of a grid filled with different coloured squares ('pixels') which make up the image, in the same way that a mosaic consisting of tiles will make up a picture when looked at from a distance.

Bitmap

Files stored in this way are referred to as a bitmapped files (this can be confusing, as bitmap is also the name of a type of picture file as well being the name of the way the information is stored- technically a Gif file or a jpeg file's information is bitmapped). The quality of a bitmap image when printed depends on the size of the pixels. A picture made up of very large pixels will look pretty much like a mosaic- you will be able to see a collection of squares if you examine the picture carefully, and smooth curves can seem jagged.

Resolution

As the quality of a bitmapped image is dependent on the size of the pixels, a value is needed to quantify this. Instead of defining the width of each pixel (as this number would be very small) the number of pixels per linear inch is used instead (i.e. how many pixels do you have to line up before you get a 1" line), this is referred to as the resolution. For example a 2 inch image made up of a 200 pixels will have a resolution of 10 dpi (dots per inch). This calculation is done by dividing 200 by 2 and square-routing. The higher the resolution, the bigger the file size, but also the better the print quality. Beyond a certain extreme, resolution no longer matters as the paper printed on absorbs ink and blots the image by more than the width of a pixel. The standard resolution for newspapers is about 200 to 300 dpi and for magazines about 400 to 600 dpi. This is why there are several sizes of files provided. For the Gif images provided, the file sizes are greatly reduced because the method of storage gifs use mean that they recognise large areas that are the same colour (such as the white back ground of the logo) and define whole regions as being of that hue, rather than defining the color of every single pixel individually. Also gifs operate by reducing the number of colours used in a file, making it much smaller.

Vectormap

Vectormapped images (also referred to as Objectmapped) are defined in completely different manner. Instead of breaking the image down into a series of blocks, the format involves graphics being defined by a set of lines and geometric shapes. Instead of a circle being broken into tiny squares, it is specified as a circle whose center is at a certain set of coordinates and has a specific radius. Likewise a square is defined by the coordinates of its corners etc.
This method results in very small file sizes, and creates images of infinite resolution. The drawbacks of this format are that you can't create photographic style images, only geometric shapes. As the NLCB logo is fairly geometric this is the ideal method of storing the data.

Conversions

Images can be converted between available formats by using shareware applications such as Image Explorer Pro for Windows, or Graphic Converter for Macintosh.