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The command to start graphics must be transmitted next. The command is:

<ESC> *r n A

where n can take a value ofeither Oor 1.If you enter O,the margin for graphics will be set at the left-most printable edge of the page (not the same as the left margin for text). But if you enter 1,the margin for graphics will be set at the column of the current print position, and your image will appear only to the right of that graphics margin.

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Three graphic data compression formats are available for data transfer. The data compression format to be used is selected using the following com- mand:

<ESC> *b n M

where n can take the value O, 1 or 2. Any other value is interpreted as O. A full discussion of data compression technique is outside the scope of this manual, but a brief explanation of this command should be useful.

Where n = O,no encoding takes place, and a simple binary transfer takes place. Bit 7 of the first byte corresponds to the first dot in a raster row, bit 6 to the second, and so on.

Where n = 1, run-length encoding takes place. This is a compression technique where the data is divided into pairs; the first byte of each pair serving as the repetition count for the data in the second pair. If the first byte of the pair is equal to zero, the data in the second byte is not repeated.

Where n = 2, the data to follow is in Tagged Image File Format (TIFF) conforming to rev. 4.0 standards. The demands of space do not allow a detailed discussion of TIFF standards here, but briefly, TIFF files com- bine features of non-encoded and non-encoded files. Many proprietary graphics packages use TIFF encoding when storing and transmitting graphic data.

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