huffman: small fixes

* write correct files/image sizes to header
* eol/rtc funcs in huffman.c
* align rtc on byte boundary
* doc update
* bump version to 1.6.2

API-full.md

@@ -413,20 +413,29 @@ BMP for 3- or 4-color images, call `bmpwrite_allow_2bit()` before calling
 
 Indexed images may optionally be written as RLE4 or RLE8 compressed BMPs.
 Images with 16 or fewer colors can be written as either RLE4 or RLE8
-(default is RLE4), images with more than 16 colors only as RLE8.
+(default is RLE4), images with more than 16 colors only as RLE8. Images with
+only 2 colors can also be written with 1-D Huffman encoding, but only
+after explicitly allowing it by calling `bmpwrite_allow_huffman()`.
 
 To activate RLE compression, call
 
 ```
 BMPRESULT bmpwrite_set_rle(BMPHANDLE h, BMPRLETYPE type)
+BMPRESULT bmpwrite_allow_huffman(BMPHANDLE h)
 ```
 
 with `type` set to one of the following values:
 - `BMP_RLE_NONE` no RLE compression, same as not calling `bmpwrite_set_rle()`
   at all
-- `BMP_RLE_AUTO` choose RLE4 or RLE8 based on number of colors in palette
+- `BMP_RLE_AUTO` choose RLE4, RLE8, or 1-D Huffman based on number of colors
+  in palette
 - `BMP_RLE_RLE8` use RLE8, regardless of number of colors in palette
 
+In order to write 1-D Huffman encoded bitmpas, the provided palette must have
+2 colors, rle type must be set to `BMP_RLE_AUTO`, and `bmpwrite_allow_huffman
+()` must be called. Be aware that *very* few programs will be able to read
+Huffman encoded BMPs!
+
 
 ### top-down / bottom-up
 

README.md

@@ -8,7 +8,7 @@
 
 Download [bmplib on github](https://github.com/rupertwh/bmplib).
 
-## Current status (v1.6.1):
+## Current status (v1.6.2):
 ### Reading BMP files:
   - 16/24/32 bit RGB(A) with any bits/channel combination
     (BI_RGB, BI_BITFIELDS, BI_ALPHABITFIELDS).
@@ -38,6 +38,7 @@ Download [bmplib on github](https://github.com/rupertwh/bmplib).
   - 64-bit RGBA
   - any bit-depth combination for the RGBA channels.
   - Indexed 1/2/4/8 bit, optional RLE4 and RLE8 compression.
+  - HUffman encoded (OS/2).
   - write BI_RGB when possible, BI_BITFIELDS only when
     necessary.
   - optional line-by-line writing of BMPs.
@@ -86,7 +87,7 @@ Includes:
 #include <bmplib.h>
 ```
 
-see API.md for the API documentation
+see API-quick-start.md and API-full.md for the API documentation
 
 
 ### 64bit BMPs

bmp-write.c

@@ -244,7 +244,7 @@ API BMPRESULT bmpwrite_set_palette(BMPHANDLE h, int numcolors,
 	if (!s_is_setting_compatible(wp, "indexed"))
 		return BMP_RESULT_ERROR;
 
-	if (numcolors < 1 || numcolors > 256) {
+	if (numcolors < 2 || numcolors > 256) {
 		logerr(wp->log, "Invalid number of colors for palette (%d)",
 		                                          numcolors);
 		return BMP_RESULT_ERROR;
@@ -607,8 +607,7 @@ static void s_decide_outformat(BMPWRITE_R wp)
 				wp->rle = 8;
 				wp->ih->compression = BI_RLE8;
 				wp->ih->bitcount = 8;
-			} else if (wp->palette->numcolors > 2 ||
-			           !wp->allow_huffman) {
+			} else if (wp->palette->numcolors > 2 || !wp->allow_huffman) {
 				wp->rle = 4;
 				wp->ih->compression = BI_RLE4;
 				wp->ih->bitcount = 4;
@@ -727,9 +726,6 @@ API BMPRESULT bmpwrite_save_image(BMPHANDLE h, const unsigned char *image)
 	wp->saveimage_done = TRUE;
 	wp->bytes_written_before_bitdata = wp->bytes_written;
 
-	if (wp->ih->compression == BI_OS2_HUFFMAN)
-		huff_encode(wp, -1, 0); /* leading eol */
-
 	linesize = (size_t) wp->width * wp->source_bytes_per_pixel;
 	for (y = 0; y < wp->height; y++) {
 		real_y = (wp->outorientation == BMP_ORIENT_TOPDOWN) ? y : wp->height - y - 1;
@@ -762,14 +758,11 @@ API BMPRESULT bmpwrite_save_image(BMPHANDLE h, const unsigned char *image)
 			}
 		}
 		else {
-			huff_encode(wp, -1, 0);
-			huff_encode(wp, -1, 0);
-			huff_encode(wp, -1, 0);
-			huff_encode(wp, -1, 0);
-			huff_encode(wp, -1, 0);
-			huff_flush(wp);
+			if (!(huff_encode_rtc(wp) && huff_flush(wp))) {
+				logsyserr(wp->log, "Writing RTC end-of-file marker");
+				return BMP_RESULT_ERROR;
+			}
 		}
-
 		s_try_saving_image_size(wp);
 	}
 
@@ -799,8 +792,6 @@ API BMPRESULT bmpwrite_save_line(BMPHANDLE h, const unsigned char *line)
 			goto abort;
 		wp->bytes_written_before_bitdata = wp->bytes_written;
 		wp->line_by_line = TRUE;
-		if (wp->ih->compression == BI_OS2_HUFFMAN)
-			huff_encode(wp, -1, 0); /* leading eol */
 	}
 
 	switch (wp->rle) {
@@ -830,12 +821,10 @@ API BMPRESULT bmpwrite_save_line(BMPHANDLE h, const unsigned char *line)
 					goto abort;
 				}
 			} else {
-				huff_encode(wp, -1, 0);
-				huff_encode(wp, -1, 0);
-				huff_encode(wp, -1, 0);
-				huff_encode(wp, -1, 0);
-				huff_encode(wp, -1, 0);
-				huff_flush(wp);
+				if (!(huff_encode_rtc(wp) && huff_flush(wp))) {
+					logsyserr(wp->log, "Writing RTC end-of-file marker");
+					goto abort;
+				}
 			}
 			s_try_saving_image_size(wp);
 		}
@@ -1233,23 +1222,21 @@ static int s_save_line_rle4(BMPWRITE_R wp, const unsigned char *line)
 
 static int s_save_line_huff(BMPWRITE_R wp, const unsigned char *line)
 {
-	int x, len, total = 0;
+	int x = 0, len;
 	int black = FALSE;
 
-	x = 0;
+	if (!huff_encode_eol(wp)) /* each line starts with eol */
+		goto abort;
+
 	while (x < wp->width) {
 		len = 0;
 		while ((len < wp->width - x) && ((!!line[x + len]) == black))
 			len++;
 		if (!huff_encode(wp, len, black))
 			goto abort;
-		total += len;
 		black = !black;
 		x += len;
 	}
-	if (!huff_encode(wp, -1, 0)) /* eol */
-		goto abort;
-
 	return TRUE;
 abort:
 	logsyserr(wp->log, "Writing 1-D Huffman data to BMP file");

huffman.c

@@ -36,7 +36,7 @@
 
 
 static int s_findnode(uint32_t bits, int nbits, int black, int *found);
-
+static int s_zerofill(BMPWRITE_R wp);
 
 
 /*****************************************************************************
@@ -116,6 +116,11 @@ void huff_fillbuf(BMPREAD_R rp)
 }
 
 
+
+/*****************************************************************************
+ * s_push()
+ ****************************************************************************/
+
 static int s_push(BMPWRITE_R wp, int bits, int nbits)
 {
 	if (nbits > 32 - wp->hufbuf_len) {
@@ -130,6 +135,10 @@ static int s_push(BMPWRITE_R wp, int bits, int nbits)
 
 
 
+/*****************************************************************************
+ * huff_encode()
+ ****************************************************************************/
+
 int huff_encode(BMPWRITE_R wp, int val, int black)
 {
 	const struct Huffcode *makeup, *term;
@@ -159,6 +168,59 @@ int huff_encode(BMPWRITE_R wp, int val, int black)
 	return TRUE;
 }
 
+
+
+/*****************************************************************************
+ * huff_encode_eol()
+ ****************************************************************************/
+
+int huff_encode_eol(BMPWRITE_R wp)
+{
+	return huff_encode(wp, -1, 0);
+}
+
+
+
+/*****************************************************************************
+ * huff_encode_rtc()
+ ****************************************************************************/
+
+int huff_encode_rtc(BMPWRITE_R wp)
+{
+	if (!s_zerofill(wp))
+		return FALSE;
+
+	for (int i = 0; i < 6; i++) {
+		if (!huff_encode_eol(wp))
+			return FALSE;
+	}
+	return TRUE;
+}
+
+
+
+/*****************************************************************************
+ * s_zerofill()
+ *
+ * add fill 0s up to next byte boundary
+ ****************************************************************************/
+
+static int s_zerofill(BMPWRITE_R wp)
+{
+	int n = 8 - wp->hufbuf_len % 8;
+
+	if (n < 8)
+		return s_push(wp, 0, n);
+
+	return TRUE;
+}
+
+
+
+/*****************************************************************************
+ * huff_flush()
+ ****************************************************************************/
+
 int huff_flush(BMPWRITE_R wp)
 {
 	int byte;
@@ -169,6 +231,7 @@ int huff_flush(BMPWRITE_R wp)
 			logsyserr(wp->log, "writing Huffman bitmap");
 			return FALSE;
 		}
+		wp->bytes_written++;
 		wp->hufbuf_len -= 8;
 		wp->hufbuf &= (1UL << wp->hufbuf_len) - 1;
 	}

huffman.h

@@ -22,4 +22,6 @@ int huff_decode(BMPREAD_R rp, int black);
 void huff_fillbuf(BMPREAD_R rp);
 
 int huff_encode(BMPWRITE_R wp, int val, int black);
+int huff_encode_eol(BMPWRITE_R wp);
+int huff_encode_rtc(BMPWRITE_R wp);
 int huff_flush(BMPWRITE_R wp);

meson.build

@@ -1,4 +1,4 @@
-project('bmplib', 'c', default_options: ['c_std=c11'], version: '1.6.1')
+project('bmplib', 'c', default_options: ['c_std=c11'], version: '1.6.2')
 
 cc = meson.get_compiler('c')