Add readme for example programs.

.gitignore

@@ -8,7 +8,9 @@
 /autom4te.cache
 /config.log
 /config.status
+/configure~
 /doc/pdfio.epub
+/examples/code128
 /Makefile
 /packages
 /pdfio.pc

EXAMPLES.md

@@ -0,0 +1,11 @@
+PDFio Examples
+==============
+
+The "examples" subdirectory contains example code showing how to do different
+things with PDFio.
+
+
+code128.c
+---------
+
+This example shows how to embed and use a barcode font.

examples/code128.c

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+//
+// Code 128 barcode example for PDFio.
+//
+// Copyright © 2024 by Michael R Sweet.
+//
+// Licensed under Apache License v2.0.  See the file "LICENSE" for more
+// information.
+//
+// Usage:
+//
+//   ./code128 "BARCODE" ["TEXT"] >FILENAME.pdf
+//
+
+#include <pdfio.h>
+#include <pdfio-content.h>
+
+
+//
+// 'make_code128()' - Make a Code 128 barcode string.
+//
+// This function produces a Code B (printable ASCII) representation of the
+// source string and doesn't try to optimize using Code C.  Non-printable and
+// extended characters are ignored in the source string.
+//
+
+
+static char *				// O - Output string
+make_code128(char       *dst,		// I - Destination buffer
+             const char *src,		// I - Source string
+             size_t     dstsize)	// I - Size of destination buffer
+{
+  char		*dstptr,		// Pointer into destination buffer
+		*dstend;		// End of destination buffer
+  int		sum = 0;		// Weighted sum
+  static const char *code128_chars =	// Code 128 characters
+		" !\"#$%&'()*+,-./0123456789:;<=>?"
+		"@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_"
+		"`abcdefghijklmnopqrstuvwxyz{|}~\303"
+		"\304\305\306\307\310\311\312";
+  static const char code128_fnc_3 = '\304';
+					// FNC 3
+  static const char code128_fnc_2 = '\305';
+					// FNC 2
+  static const char code128_shift_b = '\306';
+					// Shift B (for lowercase)
+  static const char code128_code_c = '\307';
+					// Code C
+  static const char code128_code_b = '\310';
+					// Code B
+  static const char code128_fnc_4 = '\311';
+					// FNC 4
+  static const char code128_fnc_1 = '\312';
+					// FNC 1
+  static const char code128_start_code_a = '\313';
+					// Start code A
+  static const char code128_start_code_b = '\314';
+					// Start code A
+  static const char code128_start_code_c = '\315';
+					// Start code A
+  static const char code128_stop = '\316';
+					// Stop pattern
+
+
+  // Start a Code B barcode...
+  dstptr = dst;
+  dstend = dst + dstsize - 3;
+
+  *dstptr++ = code128_start_code_b;
+  sum       = code128_start_code_b - 100;
+
+  while (*src && dstptr < dstend)
+  {
+    if (*src >= ' ' && *src < 0x7f)
+    {
+      sum       += (dstptr - dst) * (*src - ' ');
+      *dstptr++ = *src;
+    }
+
+    src ++;
+  }
+
+  // Add the weighted sum modulo 103
+  *dstptr++ = code128_chars[sum % 103];
+
+  // Add the stop pattern and return...
+  *dstptr++ = code128_stop;
+  *dstptr   = '\0';
+
+  return (dst);
+}
+
+
+//
+// 'output_cb()' - Write PDF data to the standard output...
+//
+
+static ssize_t				// O - Number of bytes written
+output_cb(void       *output_cbdata,	// I - Callback data (not used)
+          const void *buffer,		// I - Buffer to write
+          size_t     bytes)		// I - Number of bytes to write
+{
+  (void)output_cbdata;
+
+  return ((ssize_t)fwrite(buffer, 1, bytes, stdout));
+}
+
+
+//
+// 'main()' - Produce a single-page barcode file.
+//
+
+int					// O - Exit status
+main(int  argc,				// I - Number of command-line arguments
+     char *argv[])			// I - Command-line arguments
+{
+  const char	*barcode,		// Barcode to show
+		*text;			// Text to display under barcode
+  pdfio_file_t	*pdf;			// Output PDF file
+  pdfio_obj_t	*barcode_font;		// Barcode font object
+  pdfio_obj_t	*text_font = NULL;	// Text font object
+  pdfio_dict_t	*page_dict;		// Page dictionary
+  pdfio_rect_t	media_box;		// Media/CropBox for page
+  pdfio_stream_t *page_st;		// Page stream
+  char		barcode_temp[256];	// Barcode buffer
+  double	barcode_height = 36.0,	// Height of barcode
+		barcode_width,		// Width of barcode
+		text_height = 0.0,	// Height of text
+		text_width = 0.0;	// Width of text
+
+
+  // Get the barcode and optional text from the command-line...
+  if (argc < 2 || argc > 3)
+  {
+    fputs("Usage: code128 \"BARCODE\" [\"TEXT\"] >FILENAME.pdf\n", stderr);
+    return (1);
+  }
+
+  barcode = argv[1];
+  text    = argv[2];
+
+  // Output a PDF file to the standard output...
+#ifdef _WIN32
+  setmode(1, O_BINARY);			// Force binary output on Windows
+#endif // _WIN32
+
+  if ((pdf = pdfioFileCreateOutput(output_cb, /*output_cbdata*/NULL, /*version*/NULL, /*media_box*/NULL, /*crop_box*/NULL, /*error_cb*/NULL, /*error_data*/NULL)) == NULL)
+    return (1);
+
+  // Load fonts...
+  barcode_font = pdfioFileCreateFontObjFromFile(pdf, "code128.ttf", /*unicode*/false);
+  if (text)
+    text_font = pdfioFileCreateFontObjFromFile(pdf, "../testfiles/OpenSans-Regular.ttf", /*unicode*/true);
+
+  // Generate Code128 characters for the desired barcode...
+  if (!(barcode[0] & 0x80))
+    barcode = make_code128(barcode_temp, barcode, sizeof(barcode_temp));
+
+  // Compute sizes of the text...
+  barcode_width = pdfioContentTextMeasure(barcode_font, barcode, barcode_height);
+  if (text && text_font)
+  {
+    text_height = 9.0;
+    text_width  = pdfioContentTextMeasure(text_font, text, text_height);
+  }
+
+  // Compute the size of the PDF page...
+  media_box.x1 = 0.0;
+  media_box.y1 = 0.0;
+  media_box.x2 = (barcode_width > text_width ? barcode_width : text_width) + 18.0;
+  media_box.y2 = barcode_height + text_height + 18.0;
+
+  // Start a page for the barcode...
+  page_dict = pdfioDictCreate(pdf);
+
+  pdfioDictSetRect(page_dict, "MediaBox", &media_box);
+  pdfioDictSetRect(page_dict, "CropBox", &media_box);
+
+  pdfioPageDictAddFont(page_dict, "B128", barcode_font);
+  if (text_font)
+    pdfioPageDictAddFont(page_dict, "TEXT", text_font);
+
+  page_st = pdfioFileCreatePage(pdf, page_dict);
+
+  // Draw the page...
+  pdfioContentSetStrokeColorGray(page_st, 0.0);
+
+  pdfioContentSetTextFont(page_st, "B128", barcode_height);
+  pdfioContentTextBegin(page_st);
+  pdfioContentTextMoveTo(page_st, 0.5 * (media_box.x2 - barcode_width), 9.0 + text_height);
+  pdfioContentTextShow(page_st, /*unicode*/false, barcode);
+  pdfioContentTextEnd(page_st);
+
+  if (text && text_font)
+  {
+    pdfioContentSetTextFont(page_st, "TEXT", text_height);
+    pdfioContentTextBegin(page_st);
+    pdfioContentTextMoveTo(page_st, 0.5 * (media_box.x2 - text_width), 9.0);
+    pdfioContentTextShow(page_st, /*unicode*/true, text);
+    pdfioContentTextEnd(page_st);
+  }
+
+  pdfioStreamClose(page_st);
+
+  // Close and return...
+  pdfioFileClose(pdf);
+
+  return (0);
+}
+