X-Git-Url: http://git.tdb.fi/?p=ttf2png.git;a=blobdiff_plain;f=ttf2png.c;h=b8f48a816c712612049dd21b0ee2b41fc3e83c16;hp=3685b5a106d9e3f9641051b13df4dfaa8ac5aeb1;hb=3722474e4fb8de564a4952e4cff24b926bc82743;hpb=b8ace0a40f3cad1d0b56568c4ac61d63dbd190d9

diff --git a/ttf2png.c b/ttf2png.c
index 3685b5a..b8f48a8 100644
--- a/ttf2png.c
+++ b/ttf2png.c
@@ -267,18 +267,18 @@ void usage()
 		"Distributed under the GNU General Public License\n\n"
 		"Usage: ttf2png [options] <TTF file>\n\n"
 		"Accepted options (default values in [brackets])\n"
-		"  -r  Range of characters to convert in the format low,high [0,255]\n"
+		"  -r  Range of characters to convert [0,255]\n"
 		"  -s  Font size to use, in pixels [10]\n"
 		"  -l  Number of characters to put in one line [auto]\n"
 		"  -c  Character cell size, in pixels [auto]\n"
 		"  -o  Output file name (or - for stdout) [font.png]\n"
 		"  -a  Force autohinter\n"
-		"  -t  Render font to alpha channel\n"
+		"  -t  Render glyphs to alpha channel\n"
 		"  -i  Invert colors of the glyphs\n"
 		"  -v  Increase the level of verbosity\n"
-		"  -e  Use cells in sequence, rather than by code\n"
+		"  -e  Use cells in sequence, without gaps\n"
 		"  -p  Pack the glyphs tightly instead of in a grid\n"
-		"  -d  Write a definition to the given file\n"
+		"  -d  File name for writing glyph definitions\n"
 		"  -h  Print this message\n");
 }
 
@@ -339,6 +339,9 @@ void init_font(Font *font, FT_Face face, unsigned first, unsigned last, int auto
 		glyph->offset_y = face->glyph->bitmap_top-bmp->rows;
 		glyph->advance = (int)(face->glyph->advance.x+32)/64;
 
+		/* Copy the glyph image since FreeType uses a global buffer, which would
+		be overwritten by the next glyph.  Negative pitch means the scanlines
+		start from the bottom */
 		if(bmp->pitch<0)
 		{
 			for(y=0; y<bmp->rows; ++y) for(x=0; x<bmp->width; ++x)
@@ -362,6 +365,7 @@ void render_grid(Font *font, unsigned cellw, unsigned cellh, unsigned cpl, int s
 	unsigned first, last;
 	unsigned maxw = 0, maxh = 0;
 
+	/* Find extremes of the glyph images. */
 	for(i=0; i<font->n_glyphs; ++i)
 	{
 		int y;
@@ -379,6 +383,7 @@ void render_grid(Font *font, unsigned cellw, unsigned cellh, unsigned cpl, int s
 
 	if(cellw==0)
 	{
+		/* Establish a large enough cell to hold all glyphs in the range. */
 		int square = (cellh==cellw);
 		cellw = maxw;
 		cellh = top-bot;
@@ -402,6 +407,8 @@ void render_grid(Font *font, unsigned cellw, unsigned cellh, unsigned cpl, int s
 
 	if(cpl==0)
 	{
+		/* Determine number of characters per line, trying to fit all the glyphs
+		in a square image. */
 		for(i=1;; i<<=1)
 		{
 			cpl = i/cellw;
@@ -462,9 +469,12 @@ void render_packed(Font *font)
 	unsigned cx = 0, cy;
 	unsigned used_h = 0;
 
+	/* Compute the total area occupied by glyphs and padding. */
 	for(i=0; i<font->n_glyphs; ++i)
 		area += (font->glyphs[i].image.w+1)*(font->glyphs[i].image.h+1);
 
+	/* Find an image size that's no higher than wide, allowing for some
+	imperfections in the packing. */
 	for(font->image.w=1;; font->image.w<<=1)
 	{
 		font->image.h = (area*5/4)/font->image.w;
@@ -473,6 +483,10 @@ void render_packed(Font *font)
 	}
 	font->image.h = round_to_pot(font->image.h);
 
+	/* Allocate arrays for storing the image and keeping track of used pixels and
+	glyphs.  Since glyphs are rectangular and the image is filled starting from
+	the top, it's enough to track the number of used pixels at the top of each
+	column. */
 	font->image.data = (char *)malloc(font->image.w*font->image.h);
 	memset(font->image.data, 255, font->image.w*font->image.h);
 	used_pixels = (unsigned *)malloc(font->image.w*sizeof(unsigned));
@@ -488,6 +502,8 @@ void render_packed(Font *font)
 		unsigned best_score = 0;
 		unsigned target_h = 0;
 
+		/* Find the leftmost free pixel on this row.    Also record the lowest extent of glyphs
+		to the left of the free position. */
 		for(; (cx<font->image.w && used_pixels[cx]>cy); ++cx)
 			if(used_pixels[cx]-cy-1>target_h)
 				target_h = used_pixels[cx]-cy-1;
@@ -499,8 +515,10 @@ void render_packed(Font *font)
 			continue;
 		}
 
+		/* Count the free pixel at this position. */
 		for(w=0; (cx+w<font->image.w && used_pixels[cx+w]<=cy); ++w) ;
 
+		/* Find a suitable glyph to put here. */
 		for(i=0; i<font->n_glyphs; ++i)
 		{
 			Glyph *g;
@@ -510,6 +528,9 @@ void render_packed(Font *font)
 			{
 				unsigned score;
 
+				/* Prefer glyphs that would reach exactly as low as the ones left
+				of here.  This aims to create a straight edge at the bottom for
+				lining up further glyphs. */
 				score = g->image.h+1;
 				if(g->image.h==target_h)
 					score *= g->image.w;
@@ -552,6 +573,8 @@ void render_packed(Font *font)
 			used_h = cy+glyph->image.h;
 	}
 
+	/* Trim the image to the actually used size, in case the original estimate
+	was too pessimistic. */
 	font->image.h = round_to_pot(used_h);
 }
 
@@ -567,7 +590,11 @@ int save_defs(const char *fn, const Font *font)
 		return -1;
 	}
 
+	fprintf(out, "# Image/font info:\n");
+	fprintf(out, "# width height size ascent descent\n");
 	fprintf(out, "%d %d %d %d %d\n", font->image.w, font->image.h, font->size, font->ascent, font->descent);
+	fprintf(out, "\n# Glyph info:\n");
+	fprintf(out, "# code x y width height offset_x offset_y advance\n");
 	for(i=0; i<font->n_glyphs; ++i)
 	{
 		const Glyph *g = &font->glyphs[i];