Spectrum ROM | Routines |
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Used by the routine at S_POINT.
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. |
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