Raster Scaling
Raster scaling provides the ability to enlarge or reduce raster images using the Destination Raster Width and Destination Raster Height commands. The Start Raster command (?*r#A) with a value field of 2 or 3 turns on scale mode. Scaling is independent of device resolution.
Note | To use raster scaling, the Configure Image Data command (?*r#W) |
| must be sent prior to the Start Raster command (?*r#A), which must |
| have a value field of 2 or 3 to enable scaling. |
| There are two types of raster scaling: Resolution and Arbitrary. The |
| |
| scaling type is selected by the argument to the Start Raster |
| command. If either 0 or 1 are used then resolution scaling is |
| performed. If either 2 or 3 is used then arbitrary scaling is performed. |
| Resolution Scaling |
| This scaling is performed using the raster resolution in combination |
| with the device resolution. For example, if the raster resolution is set |
| to 300 dpi and the device resolution is 600 dpi, then the image is |
| scaled by a factor of two. This type of scaling does not depend on the |
| source or destination raster dimensions. |
| Arbitrary Scaling |
| This scaling is performed without regard to the raster resolution which |
| is unaffected by scale calculations. The scaling factor is determined |
| by the source and destination raster dimensions. If the destination |
| dimensions are not specified the graphics margin and printable area |
| are used to calculated destination dimensions while maintaining |
| isotropic scaling so that the entire image fits on the page. If only one |
| destination boundary is specified the other is calculated to maintain |
| isotropic scaling. |
| The destination width and height commands accept real numbers |
| with up to four decimal places of precision. This level of precision is |
| necessary when converting from decipoints to pixels so that round off |
| errors will not create visible print artifacts such as lines within the |
| image. |
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