clean up ppm viewer program

ppm viewer/README.md

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+# PPM image viewer
+
+Reads a ppm image from an input device (AF.dev by default) 
+and displays it on SicTools builtin graphical screen.
+
+To resize and convert your image you can use ffmpeg:
+```{sh}
+ffmpeg -i image.png -vf scale="64x-1" AF.ppm && mv AF.ppm AF.dev
+```
+
+- Source code: ppm.asm
+- Graphical screen: 64x64 at A000
+  - dimensions can be adjusted by changing their values in code
+- Frequency: any
+- Author: Jakob Jesenko, 2026
+

ppm viewer/ppm.asm

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+.
+. ppm.asm - prgram for dispaying of ppm images
+. 
+. notice: any overflow of graphical screen is also
+.   copied to memory however only top left (64x64 pixels)
+.   remain visible
+.
+. default values from Sictools:
+.   - Graphical screen address: 0x00A000
+.   - Columns:                  64
+.   - Rows:                     64
+. default input device inputd:  0xAF
+.
+
+
+ppm	START	0
+	LDA	#stack  . setup stack
+	STA	sp
+	CLEAR	B
+hloop	CLEAR	A       . write image metadata to stdout
+	RD	inputd
+	WD	#1
+	COMP	#10
+	JEQ	ln2
+	J	hloop
+ln2	CLEAR	A
+	RD	inputd
+	COMP	#35	.#
+	JEQ	comm
+	J	dims1
+comm	WD	#1
+ln2lp	CLEAR	A
+	RD	inputd
+	WD	#1
+	COMP	#10
+	JEQ	dims
+	J	ln2lp
+dims	RD	inputd
+dims1	COMP	#32
+	JEQ	dims1e
+	WD	#1
+	SUB	#48	.0
+	ADDR	A,B
+	LDA	#10
+	MULR	A,B
+	RD	inputd
+	J	dims1
+dims1e	WD	#1
+	LDA	#10
+	DIVR	A,B
+	STB	width
+	CLEAR	B
+	RD	inputd
+dims2	COMP	#10
+	JEQ	dims2e
+	WD	#1
+	SUB	#48	.0
+	ADDR	A,B
+	LDA	#10
+	MULR	A,B
+	RD	inputd
+	J	dims2
+dims2e	WD	#1
+	LDA	#10
+	DIVR	A,B
+	STB	height
+	CLEAR	B
+	RD	inputd
+dims3	COMP	#10
+	JEQ	dims3e
+	WD	#1
+	SUB	#48	.0
+	ADDR	A,B
+	LDA	#10
+	MULR	A,B
+	RD	inputd
+	J	dims3
+dims3e	WD	#1
+	LDA	#10
+	DIVR	A,B
+	STB	maxval
+	CLEAR	B
+	
+	LDA	width
+	MUL	height
+	STA	pixcnt
+
+mainlp	CLEAR	A
+	CLEAR	B
+	RD	inputd  . read color data for one pixel
+	STCH	red
+	RD	inputd
+	STCH	green
+	RD	inputd
+	STCH	blue
+	JSUB	intens  . calculate color intensity
+	LDCH	clrmax
+	DIV	#64     . construct pixel color according to
+	ADDR	A,B     .   graphical screen specification
+	SHIFTL	B,2
+	LDCH	red
+	DIV	#64
+	ADDR	A,B
+	SHIFTL	B,2
+	LDCH	green
+	DIV	#64
+	ADDR	A,B
+	SHIFTL	B,2
+	LDCH	blue
+	DIV	#64
+	ADDR	B,A
+
+	STCH	@pixptr . print pixel to graphical screen
+	LDA	pixptr  . calculate next pixel position
+	ADD	#1
+	STA	pixptr
+	LDA	pixctr
+	ADD	#1
+	STA	pixctr
+	DIV	width
+	MUL	width
+	COMP	pixctr
+	JEQ	ptradj  . reset position to first column
+adjret	
+
+
+	LDA	pixctr  . check if all pixels have been 
+	COMP	pixcnt  .   displayed
+	JEQ	halt
+	J	mainlp
+	J	halt
+
+ptradj	LDA	pixptr
+	SUB	width
+	ADD	cols
+	STA	pixptr
+	J	adjret
+
+
+halt	J	halt
+
+. calculate color intensity by extracting
+.   color component, that has the highest
+.   value
+.   this might not be the correct algorhitm,
+.   but produces adequate results
+intens	STA	@sp     . push registers
+	LDA	sp
+	ADD	#3
+	STA	sp
+	STB	@sp
+	ADD	#3
+	STA	sp
+	...
+	CLEAR	A
+	LDA	red
+	COMP	green
+	JLT	swpgrn
+retgrn	COMP	blue
+	JLT	swpblu
+retblu	STA	clrmax
+	...
+	LDA	sp      . pop registers
+	SUB	#3
+	STA	sp
+	LDB	@sp
+	SUB	#3
+	STA	sp
+	LDA	@sp
+	RSUB
+swpgrn	LDA	green
+	J	retgrn
+swpblu	LDA	blue
+	J	retblu
+
+	
+inputd	BYTE	X'AF'
+width	RESW	1
+height	RESW	1
+maxval	RESW	1
+pixcnt	RESW	1
+rows	WORD	64
+cols	WORD	64
+pixptr	WORD	X'00A000'
+screen	WORD	X'00A000'
+pixctr	WORD	0
+srtptr	RESW	1
+red	RESW	1
+green	RESW	1
+blue	RESW	1
+clrmax	RESW	1
+sp	RESW	1
+stack	RESW	1024
+
+	END	ppm