shithub: subpixelize

--- a/README

+++ b/README

@@ -7,24 +7,27 @@

 This program converts a grayscale image to a colored image that makes use of subpixels to add fine details.

-The program defines three levels of gray:

+The program expects an image three times the size of the target image. Each group of 3x3 pixels will be converted to a single pixel that is composed out of the three subpixels.

-- Black: <  64

-- Low:   ≥  64 and < 128

-- High:  ≥ 128 and < 192

-- White: ≥ 192

+It is possible to scale the value by using grayscale values. The subpixel will be filled with the average value of its column. For example, both

-Depending on the surrounding two pixels (left and right), Low and High values will be replaced by colored pixels.

+000 128 000

+000 128 000

+000 128 000

+and

-BUGS

+000 255 000

+000 128 000

+000 000 000

-Right now, the input image needs to have 3 or 4 channels (alpha is ignored/will be passed through). Single-channel images must be converted before use, e. g. using iconv.

+will be converted to rgb(0, 128, 0).

-Only images with (mostly) pure black and (mostly) pure white areas are supported.

+BUGS

+The groups of 3x3 pixels need to be aligned to the grid.

 Subpixelize supports only horizontal subpixels (RGB in a row).

 Some people don't like subpixels.

-The quality of the results isn't visually perfect and might need manual fixup.

--- a/mkfile

+++ b/mkfile

@@ -7,4 +7,4 @@

 </sys/src/cmd/mkone

 t:V: $O.out

-	$O.out < test.bit > testout.bit

+	$O.out < sand.bit > sandout.bit

binary files /dev/null b/sand.bit differ

--- a/subpixelize.c

+++ b/subpixelize.c

@@ -3,189 +3,68 @@

 #include <draw.h>

 #include <memdraw.h>

-void

-usage(void)

+static void

+transformpx(Memimage *src, Memimage *dst, Point p)

-	fprint(2, "usage: %s\n", argv0);

-	exits("usage");

-}

-#define LOWVAL   (255/4)

-#define HIGHVAL  (255/4*3)

-#define LOW(A)   ((A) >= LOWVAL && (A) < 128)

-#define HIGH(A)  ((A) < HIGHVAL && (A) >= 128)

-#define BLACK(A)  ((A) < LOWVAL)

-#define WHITE(A) ((A) >= HIGHVAL)

-typedef enum {

-	Equal,

-	Low,

-	High,

-	Rise,

-	Fall,

-} Type;

-int

-getbyteval(uchar *val, int nchan)

-{

-	int v, i;

+	uchar *t;

+	uchar *s1, *s2, *s3;

+	uchar *s4, *s5, *s6;

+	uchar *s7, *s8, *s9;

-	v = 0;

-	for (i = 0; i < nchan-1; i++)

-		v += val[i];

+	t = byteaddr(dst, p);

-	return v/i;

-}

-Type

-checkrow(Memimage *src, Point p2, uchar *ival)

-{

-	Point p1, p3;

-	int v1, v2, v3;

+	p.x *= 3;

+	p.y *= 3;

-	p1 = p2;

-	p3 = p2;

-	p1.x--;

-	p3.x++;

+	s1 = byteaddr(src, Pt(p.x  , p.y  ));

+	s2 = byteaddr(src, Pt(p.x+1, p.y  ));

+	s3 = byteaddr(src, Pt(p.x+2, p.y  ));

+	s4 = byteaddr(src, Pt(p.x  , p.y+1));

+	s5 = byteaddr(src, Pt(p.x+1, p.y+1));

+	s6 = byteaddr(src, Pt(p.x+2, p.y+1));

+	s7 = byteaddr(src, Pt(p.x  , p.y+2));

+	s8 = byteaddr(src, Pt(p.x+1, p.y+2));

+	s9 = byteaddr(src, Pt(p.x+2, p.y+2));

-	if (!ptinrect(p1, src->r))

-		return Equal;

-	if (!ptinrect(p2, src->r))

-		return Equal;

-	if (!ptinrect(p3, src->r))

-		return Equal;

-	v1 = getbyteval(byteaddr(src, p1), src->nchan);

-	v2 = getbyteval(byteaddr(src, p2), src->nchan);

-	v3 = getbyteval(byteaddr(src, p3), src->nchan);

-	*ival = v2;

-	if (BLACK(v2) || WHITE(v2))

-		return Equal;

-	if (BLACK(v1) && BLACK(v3))

-		return Low;

-	if (WHITE(v1) && WHITE(v3))

-		return High;

-	if (BLACK(v1) && WHITE(v3))

-		return Rise;

-	if (WHITE(v1) && BLACK(v3))

-		return Fall;

-	if (BLACK(v1) &&   LOW(v3))

-		return Rise;

-	if (BLACK(v1) &&  HIGH(v3))

-		return Rise;

-	if ( HIGH(v1) && BLACK(v3))

-		return Fall;

-	if (  LOW(v1) && BLACK(v3))

-		return Fall;

-	fprint(2, "unhandled case! %3d %3d %3d\n", v1, v2, v3);

-	return Equal;

+	t[2] = (*s1 + *s4 + *s7) / 3;

+	t[1] = (*s2 + *s5 + *s8) / 3;

+	t[0] = (*s3 + *s6 + *s9) / 3;

-void

-handlepixel(Memimage *tgt, Memimage *src, Point p)

+static void

+transform(Memimage *src, Memimage *dst)

-	uchar *t, *s;

-	int i;

-	Type tp;

-	uchar ival;

-	uchar col[4]; /* bgra */

+	int x, y;

-	t = byteaddr(tgt, p);

-	s = byteaddr(src, p);

-	for (i = 0; i < tgt->nchan; i++) {

-		t[i] = s[i];

-	}

-	tp = checkrow(src, p, &ival);

-	if (tp == Equal)

-		return;

-	if (BLACK(ival))

-		return;

-	if (WHITE(ival)) /* considered white */

-		return;

-	/* green value */

-	col[1] = LOW(ival) ? 0 : 255;

-	col[3] = 255;

-	switch (tp) {

-	case Rise:

-		//fprint(2, "case r √\n");

-		col[0] = 255;

-		col[2] =   0;

-		goto Fill;

-	case Fall:

-		//fprint(2, "case f √\n");

-		col[0] =   0;

-		col[2] = 255;

-		goto Fill;

-	case High:

-		//fprint(2, "case h √\n");

-		col[0] = 255;

-		col[1] = LOW(ival) ? 0 : 128;

-		col[2] = 255;

-		goto Fill;

-	case Low:

-		//fprint(2, "case l √\n");

-		col[0] =   0;

-		col[1] = LOW(ival) ? 128 : 255;

-		col[2] =   0;

-		goto Fill;

-	}

-	fprint(2, "should never happen!\n");

-	return;

-Fill:

-	for (i = 0; i < tgt->nchan; i++) {

-		t[i] = col[i];

-	}

+	for (y = dst->r.min.y; y < dst->r.max.y; y++)

+		for (x = dst->r.min.x; x < dst->r.max.x; x++)

+			transformpx(src, dst, Pt(x, y));

 void

-subpixelize(Memimage *tgt, Memimage *src)

+main(void)

-	long x, y;

+	Memimage *in, *out;

+	Rectangle r;

-	for (y = tgt->r.min.y; y < tgt->r.max.y; y++)

-		for (x = tgt->r.min.x; x < tgt->r.max.x; x++)

-			handlepixel(tgt, src, Pt(x, y));

-}

-void

-main(int argc, char **argv)

-{

-	Memimage *src;

-	Memimage *tgt;

-	ARGBEGIN{

-	case 'h':

-		usage();

-		break;

-	}ARGEND;

 	if (memimageinit() < 0)

 		sysfatal("%r");

-	src = readmemimage(0);

-	if (!src)

-		sysfatal("readmemimage: %r");

+	in = readmemimage(0);

+	if (!in)

+		sysfatal("%r");

-	if (!(src->nchan == 3 || src->nchan == 4))

-		sysfatal("unsupported chan");

+	r.min.x = in->r.min.x/3;

+	r.min.y = in->r.min.y/3;

+	r.max.x = r.min.x + Dx(in->r)/3;

+	r.max.y = r.min.y + Dy(in->r)/3;

-	tgt = allocmemimage(src->r, src->chan);

-	if (!tgt)

-		sysfatal("allocmemimage: %r");

-	memfillcolor(tgt, DTransparent);

+	out = allocmemimage(r, RGB24);

+	if (!out)

+		sysfatal("%r");

-	subpixelize(tgt, src);

-	if (writememimage(1, tgt) < 0)

-		sysfatal("writememimage");

+	transform(in, out);

+	writememimage(1, out);

 	exits(nil);

-}

\ No newline at end of file

+}

binary files a/test.bit /dev/null differ

--

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