Routines
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29776: Colourise Sprite
Used by the routines at DrawCubbyHoleItem, AnimateExplosion, UpdateStreamer, UpdateLeaf, UpdateFlower, UpdateSprayCan, DrawObject and UpdateBonusItem.
Writes the colour of an actor into the attribute buffer, covering the character cells that its sprite has just been drawn over. The pixels are drawn first (see DisplayEntity), so until this routine runs the sprite is drawn in the attribute that was already there.
Input
IX Actor object
Before After
colourise-before colourise-after
ColouriseSprite 29776 EXX Switch to the shadow registers.
29777 LD HL,(24090) Fetch the screen position of the sprite from SpritePosition.
29780 CALL AttributeAddress Convert it to an attribute buffer address using AttributeAddress.
29783 LD A,(24079) Set the column counter in B' to the sprite width, from NewSprite_Width.
29786 LD B,A
29787 LD A,(24078) Fetch the sprite height in pixels from 24078.
29790 RRCA Divide the height by 4 add 1 then divide by 2.
29791 RRCA
29792 INC A
29793 RRCA
29794 AND %00011111 Keep only bits 0-4.
29796 INC A Increment A by one.
29797 LD C,A Set the row counter in C' to the result.
29798 LD D,(IX+3) Fetch the colour attribute from *IX+3.
29801 LD E,B Remember the sprite width in E' so that the column counter can be reset for each row.
Colour one row of attribute cells.
ColouriseSprite_Loop1 29802 PUSH HL Stash the address of the start of the row on the stack.
ColouriseSprite_Loop2 29803 LD A,H Fetch the MSB of the attribute buffer address.
29804 CP 91 Jump to ColouriseSprite_NextRow if the address is beyond the attribute buffer (H is at least 91).
29806 JR NC,ColouriseSprite_NextRow
29808 CP 88 Jump to ColouriseSprite_NextRow if the address is before the attribute buffer (H is less than 88).
29810 JR C,ColouriseSprite_NextRow
29812 LD (HL),D Write the colour to the attribute buffer.
29813 INC L Move onto the next column.
29814 LD A,L Fetch the low byte of the address.
29815 AND %00011111 Keep only bits 0-4 (the column).
29817 JR NZ,ColouriseSprite_NextColumn Jump to ColouriseSprite_NextColumn if the column has not wrapped onto the next row.
29819 LD A,L Move back to the start of the same row of attribute cells.
29820 SUB 32
29822 LD L,A
ColouriseSprite_NextColumn 29823 DJNZ ColouriseSprite_Loop2 Decrease the column counter by one and loop back to ColouriseSprite_Loop2 until it is zero.
Move up one row of attribute cells.
ColouriseSprite_NextRow 29825 POP HL Restore the address of the start of the row from the stack.
29826 PUSH BC Subtract 32 from HL, preserving BC.
29827 AND A
29828 LD BC,32
29831 SBC HL,BC
29833 POP BC
29834 LD B,E Reset the column counter from E'.
29835 DEC C Decrease the row counter by one and loop back to ColouriseSprite_Loop1 until it is zero.
29836 JR NZ,ColouriseSprite_Loop1
29838 RET Return.
View the equivalent code in;
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