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git-svn-id: http://svn.code.sf.net/p/netpbm/code/trunk@1 9d0c8265-081b-0410-96cb-a4ca84ce46f8

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+/*\
+ * $Id: bmp.h,v 1.3 1992/11/24 19:39:56 dws Exp dws $
+ * 
+ * bmp.h - routines to calculate sizes of parts of BMP files
+ *
+ * Some fields in BMP files contain offsets to other parts
+ * of the file.  These routines allow us to calculate these
+ * offsets, so that we can read and write BMP files without
+ * the need to fseek().
+ * 
+ * Copyright (C) 1992 by David W. Sanderson.
+ * 
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation for any purpose and without fee is hereby granted,
+ * provided that the above copyright notice appear in all copies and
+ * that both that copyright notice and this permission notice appear
+ * in supporting documentation.  This software is provided "as is"
+ * without express or implied warranty.
+ * 
+ * $Log: bmp.h,v $
+ * Revision 1.3  1992/11/24  19:39:56  dws
+ * Added copyright.
+ *
+ * Revision 1.2  1992/11/17  02:13:37  dws
+ * Adjusted a string's name.
+ *
+ * Revision 1.1  1992/11/16  19:54:44  dws
+ * Initial revision
+ *
+\*/
+
+/* 
+   There is a specification of BMP (2003.07.24) at:
+
+     http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/bitmaps_4v1h.asp
+
+   There is a better written specification of the Windows BMP format
+   in (2000.06.08) <http://www.daubnet.com/formats/BMP.html>.
+   However, the "Windows BMP" format used in practice is much closer
+   to the Microsoft definition.  The Microsoft spec was not known for
+   Netpbm development until 2003.07.24.
+
+   The ColorsImportant field is defined in the daubnet spec as "Number of
+   important colors.  0 = all"  That is the entire definition.  The
+   spec also says the number of entries in the color map is a function
+   of the BitCount field alone.
+
+   But Marc Moorcroft says (2000.07.23) that he found two BMP files
+   some time ago that had a color map whose number of entries was not
+   as specified and was in fact the value of ColorsImportant.
+
+   And Bill Janssen actually produced some BMPs in January 2001 that
+   appear to have the size of the colormap determined by ColorsUsed.
+   They have 8 bits per pixel in the raster, but ColorsUsed is 4 and
+   there are in fact 4 entries in the color map.  He got these from
+   the Palm emulator for Windows, using the "Save Screen" menu 
+   option.
+
+   Bmptoppm had, for a few releases in 2000, code by Marc to use
+   ColorsImportant as the color map size unless it was zero, in which
+   case it determined color map size as specified.  The current
+   thinking is that there are probably more BMPs that need to be
+   interpreted per the spec than that need to be interpreted Marc's
+   way.  
+
+   But in light of Janssen's discovery, we have made the assumption
+   since February 2001 that when ColorsUsed is zero, the colormap size
+   is as specified, and when it is nonzero, the colormap size is given
+   by ColorsUsed.
+
+   But we were also assuming that if ColorsUsed is nonzero, the image
+   is colormapped.  We heard from "Ron & Bes Vantreese"
+   <eaglesun@aggienetwork.com> in February 2003 that his understanding
+   of the format was that ColorsUsed == 2**24 is appropriate for a
+   non-colormapped (24 bit) BMP, and images he created that way caused
+   trouble for Bmptopnm.  So since then, we look at ColorsUsed only if
+   we know because bits per pixel <= 8 that it is a colormapped image.
+
+*/
+
+#ifndef BMP_H_INCLUDED
+#define BMP_H_INCLUDED
+
+#include "pm.h"  /* For pm_error() */
+
+enum bmpClass {C_WIN=1, C_OS2=2};
+
+static char const er_internal[] = "%s: internal error!";
+
+/* Values of the "compression" field of the BMP info header */
+#define COMP_RGB       0
+#define COMP_RLE8      1
+#define COMP_RLE4      2
+#define COMP_BITFIELDS 3
+#define COMP_JPEG      4
+#define COMP_PNG       5
+
+static __inline__ unsigned int
+BMPlenfileheader(enum bmpClass const class) {
+
+    unsigned int retval;
+
+    switch (class) {
+    case C_WIN: retval = 14; break;
+    case C_OS2: retval = 14; break;
+    }
+    return retval;
+}
+
+
+
+static __inline__ unsigned int
+BMPleninfoheader(enum bmpClass const class) {
+
+    unsigned int retval;
+
+    switch (class) {
+    case C_WIN: retval = 40; break;
+    case C_OS2: retval = 12; break;
+    }
+    return retval;
+}
+
+
+
+static __inline__ unsigned int
+BMPlencolormap(enum bmpClass const class,
+               unsigned int  const bitcount, 
+               int           const cmapsize) {
+
+    unsigned int lenrgb;
+    unsigned int lencolormap;
+
+    if (bitcount < 1)
+        pm_error(er_internal, "BMPlencolormap");
+    else if (bitcount > 8) 
+        lencolormap = 0;
+    else {
+        switch (class) {
+        case C_WIN: lenrgb = 4; break;
+        case C_OS2: lenrgb = 3; break;
+        }
+
+        if (cmapsize < 0) 
+            lencolormap = (1 << bitcount) * lenrgb;
+        else 
+            lencolormap = cmapsize * lenrgb;
+    }
+    return lencolormap;
+}
+
+
+
+static __inline__ unsigned int
+BMPlenline(enum bmpClass const class,
+           unsigned int  const bitcount, 
+           unsigned int  const x) {
+/*----------------------------------------------------------------------------
+  length, in bytes, of a line of the image
+
+  Each row is padded on the right as needed to make it a multiple of 4
+  bytes int.  This appears to be true of both OS/2 and Windows BMP
+  files.
+-----------------------------------------------------------------------------*/
+    unsigned int bitsperline;
+    unsigned int retval;
+
+    bitsperline = x * bitcount;  /* tentative */
+
+    /*
+     * if bitsperline is not a multiple of 32, then round
+     * bitsperline up to the next multiple of 32.
+     */
+    if ((bitsperline % 32) != 0)
+        bitsperline += (32 - (bitsperline % 32));
+
+    if ((bitsperline % 32) != 0) {
+        pm_error(er_internal, "BMPlenline");
+        retval = 0;
+    } else 
+        /* number of bytes per line == bitsperline/8 */
+        retval = bitsperline >> 3;
+
+    return retval;
+}
+
+
+
+static __inline__ unsigned int
+BMPlenbits(enum bmpClass const class,
+           unsigned int  const bitcount, 
+           unsigned int  const x,
+           unsigned int  const y) {
+/*----------------------------------------------------------------------------
+  Return the number of bytes used to store the image bits
+  for an uncompressed image.
+-----------------------------------------------------------------------------*/
+    return y * BMPlenline(class, bitcount, x);
+}
+
+
+
+static __inline__ unsigned int
+BMPoffbits(enum bmpClass const class,
+           unsigned int  const bitcount, 
+           unsigned int  const cmapsize) {
+/*----------------------------------------------------------------------------
+  return the offset to the BMP image bits.
+-----------------------------------------------------------------------------*/
+    return BMPlenfileheader(class)
+        + BMPleninfoheader(class)
+        + BMPlencolormap(class, bitcount, cmapsize);
+}
+
+
+static __inline__ unsigned int
+BMPlenfileGen(enum bmpClass     const class,
+              unsigned int      const bitcount, 
+              int               const cmapsize,
+              unsigned int      const x,
+              unsigned int      const y,
+              unsigned int      const imageSize,
+              unsigned long int const compression) {
+/*----------------------------------------------------------------------------
+  Return the size of the BMP file in bytes.
+-----------------------------------------------------------------------------*/
+    unsigned int retval;
+
+    switch (compression) {
+    case COMP_RGB:
+    case COMP_BITFIELDS:
+        retval =
+            BMPoffbits(class, bitcount, cmapsize) +
+            BMPlenbits(class, bitcount, x, y);
+        break;
+    default:
+        retval = BMPoffbits(class, bitcount, cmapsize) + imageSize;
+    }
+    return retval;
+}
+
+
+
+static __inline__ unsigned int
+BMPlenfile(enum bmpClass const class,
+           unsigned int  const bitcount, 
+           int           const cmapsize,
+           unsigned int  const x,
+           unsigned int  const y) {
+/*----------------------------------------------------------------------------
+  return the size of the BMP file in bytes; no compression
+-----------------------------------------------------------------------------*/
+    return BMPlenfileGen(class, bitcount, cmapsize, x, y, 0, COMP_RGB);
+}
+
+#endif