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Routines |
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This subroutine is called from S_POINT. It is entered with the coordinates of a pixel on the calculator stack, and returns a last value of 1 if that pixel is ink colour, and 0 if it is paper colour.
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| POINT_SUB | 08907 | CALL STK_TO_BC | y-coordinate to B, x to C. | |
| 08910 | CALL PIXEL_ADD | Pixel address to HL. | ||
| 08913 | LD B,A | B will count A+1 loops to get the wanted bit of (HL) to location 0. | ||
| 08914 | INC B | |||
| 08915 | LD A,(HL) | |||
| POINT_LP | 08916 | RLCA | The shifts. | |
| 08917 | DJNZ POINT_LP | |||
| 08919 | AND 1 | The bit is 1 for ink, 0 for paper. | ||
| 08921 | JP STACK_A | It is put on the calculator stack. | ||
| Prev: 08874 | Up: Map | Next: 08924 |