mirror of
https://github.com/aaronsgiles/JPEGView.git
synced 2026-03-11 06:41:45 +00:00
92bdb55672
These are the sources for the final official release of JPEGView for the Mac, back in 1994.
1 line
1.9 KiB
Plaintext
1 line
1.9 KiB
Plaintext
;*********************************************************/
|
|
;* This source code copyright (c) 1991-2001, Aaron Giles */
|
|
;* See the Read Me file for licensing information. */
|
|
;* Contact email: mac@aarongiles.com */
|
|
;*********************************************************/
|
|
|
|
;
|
|
; On entry here we expect the following values:
|
|
;
|
|
; a0 = pointer to the 24-bit source pixmap row
|
|
; a1 = pointer to the 8-bit destination pixmap row
|
|
; d2 = pointer to the region buffer
|
|
; d7 = (low word) column count
|
|
;
|
|
; The following registers will be modified:
|
|
;
|
|
; d0,d1,d2,d3,d4,d5,d6,d7
|
|
; a0,a1,a3
|
|
;
|
|
; Internally, the register usage is as follows:
|
|
;
|
|
; d0 = accumulator
|
|
; d1 = accumulator
|
|
; d6 = (low word) region column counter
|
|
; d7 = (low word) column counter
|
|
;
|
|
; a0 = pointer to 24-bit source row
|
|
; a1 = pointer to 8-bit destination row
|
|
; a2 = pointer to region buffer
|
|
;
|
|
move.l d2,a2 ;and the real a2 from d2
|
|
subq.w #1,d7 ;subtract 1 from the width for dbra
|
|
;
|
|
; Set up the region column counter in d6
|
|
;
|
|
move.w (a2)+,d6 ;get region start in d6
|
|
bne.s @CopyLoop ;if not zero, skip over this business
|
|
sub.w (a2)+,d6 ;otherwise, subtract the next word
|
|
;
|
|
; Determine whether or not to draw this pixel, and handle switches
|
|
;
|
|
@CopyLoop:
|
|
tst.w d6 ;is d6 negative?
|
|
bmi.s @CopyStore ;if so, store this value
|
|
addq.w #4,a0 ;skip past the current source pixel
|
|
addq.w #4,a1 ;skip past the current dest. pixel
|
|
subq.w #1,d6 ;decrement this counter
|
|
bne.s @CopyCont ;if non-zero continue
|
|
sub.w (a2)+,d6 ;get the negative of the next value
|
|
add.w -4(a2),d6 ;and add the previous one
|
|
bra.s @CopyCont ;continue
|
|
@CopyStore:
|
|
move.l (a0)+,(a1)+ ;store the value to the output
|
|
addq.w #1,d6 ;increment the counter
|
|
bne.s @CopyCont ;if non-zero, continue
|
|
move.w (a2)+,d6 ;get the next value
|
|
sub.w -4(a2),d6 ;minus the previous
|
|
;
|
|
; End of loop: go until done
|
|
;
|
|
@CopyCont:
|
|
dbra.w d7,@CopyLoop ;loop until done
|