mirror of
https://github.com/zint/zint
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170 lines
6.0 KiB
HTML
170 lines
6.0 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
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<HTML>
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<HEAD>
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<META HTTP-EQUIV="CONTENT-TYPE" CONTENT="text/html; charset=utf-8">
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<TITLE>Making colourful barcodes</TITLE>
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</HEAD>
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<BODY LANG="en-GB" DIR="LTR">
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<TABLE WIDTH=100% BORDER=0 CELLPADDING=0 CELLSPACING=0 STYLE="page-break-before: always">
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<TR>
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<TH COLSPAN=3>
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<P ALIGN=CENTER>Zint Barcode Generator</P>
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</TH>
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</TR>
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<TR VALIGN=BOTTOM>
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<TD WIDTH=10%>
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<P ALIGN=LEFT><A HREF="appxc.html">Prev</A></P>
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</TD>
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<TD WIDTH=80%></TD>
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<TD WIDTH=10%>
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</TD>
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</TR>
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</TABLE>
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<H1>Appendix D: Making colourful barcodes</H1>
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<P>An obvious next step in the development of barcodes is to use
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colour instead of boring old black and white to encode data. This
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technique is not currently used by any barcode encoding standards in
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the wild but an indication of how it might be achieved can be gained
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with a little data processing and the Zint library.</P>
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<P>This example takes an input string and splits it into
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three roughly equal length strings each of which is encoded and then
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combined to make a colour version of the symbol. This can then be
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decoded by applying red, green and blue filters to the resulting
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image and then decoding them using the same algorithm used to decode
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normal black and white symbols as shown below.</P>
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<P ALIGN=CENTER><IMG SRC="3dprinciple.png" NAME="3dprinciple" ALIGN=CENTER WIDTH=475 HEIGHT=406 BORDER=0></P>
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<P>One advantage of this system is that finder patterns in the symbol
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show up clearly as black-on-white and so can be found using the
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methods already established for standard 2D barcodes. This can be
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clearly seen in the examples below.</P>
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<P ALIGN=CENTER><IMG SRC="3dsample.png" NAME="3dexample" ALIGN=CENTER WIDTH=416 HEIGHT=148 BORDER=0></P>
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<P>Another advantage of this system is that it fits three times as
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much data into a symbol of a given size. Disadvantages are likely to
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become apparent when trying to decode these symbols in real-world
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applications: decoding will require larger processor overheads and
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more sophisticated algorithms. Telling white from yellow may be a
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particular problem.</P>
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<P>The code below performs the encoding as done on the images above
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and outputs an array of elements as characters representing colours.
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Putting this together as an image requires additional code.</P>
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<PRE>#include <stdio.h>
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#include <zint.h>
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#include <string.h>
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int main(int argc, char **argv)
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{
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struct zint_symbol *red_symbol;
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struct zint_symbol *green_symbol;
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struct zint_symbol *blue_symbol;
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struct zint_symbol *colour_symbol;
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int error = 0;
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int i, j;
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int input_len = strlen(argv[1]);
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int snippet = input_len / 3;
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char full_string[input_len + 5];
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char red_string[(input_len / 3) + 2];
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char green_string[(input_len / 3) + 2];
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char blue_string[(input_len / 3) + 2];
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int symbol_type = BARCODE_QRCODE;
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if(input_len % 3 != 0) { snippet++; }
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strcpy(full_string, argv[1]);
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for(i = 0; i < snippet; i++) {
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red_string[i] = full_string[i];
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green_string[i] = full_string[i + snippet];
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blue_string[i] = full_string[i + snippet + snippet];
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}
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red_string[i] = '\0';
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green_string[i] = '\0';
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blue_string[i] = '\0';
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red_symbol = ZBarcode_Create();
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green_symbol = ZBarcode_Create();
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blue_symbol = ZBarcode_Create();
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colour_symbol = ZBarcode_Create();
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red_symbol->symbology = symbol_type;
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green_symbol->symbology = symbol_type;
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blue_symbol->symbology = symbol_type;
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colour_symbol->symbology = symbol_type;
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error = ZBarcode_Encode(red_symbol, (unsigned char *)red_string);
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error += ZBarcode_Encode(green_symbol, (unsigned char *)green_string);
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error += ZBarcode_Encode(blue_symbol, (unsigned char *)blue_string);
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if(error != 0) {
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printf("Some error occurred!\n");
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ZBarcode_Delete(red_symbol);
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ZBarcode_Delete(green_symbol);
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ZBarcode_Delete(blue_symbol);
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ZBarcode_Delete(colour_symbol);
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return 1;
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}
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colour_symbol->width = red_symbol->width;
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if(green_symbol->width > colour_symbol->width) { colour_symbol->width = green_symbol->width; }
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if(blue_symbol->width > colour_symbol->width) { colour_symbol->width = blue_symbol->width; }
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colour_symbol->rows = red_symbol->rows;
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if(green_symbol->rows > colour_symbol->rows) { colour_symbol->rows = green_symbol->rows; }
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if(blue_symbol->rows > colour_symbol->rows) { colour_symbol->rows = blue_symbol->rows; }
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for(i = 0; i < colour_symbol->rows; i++) {
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colour_symbol->row_height[i] = 1;
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for(j = 0; j < colour_symbol->width; j++) {
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int colourval;
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colourval = 0;
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if(red_symbol->encoded_data[i][j] == '1') { colourval += 4; }
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if(green_symbol->encoded_data[i][j] == '1') { colourval += 2; }
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if(blue_symbol->encoded_data[i][j] == '1') { colourval += 1; }
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switch(colourval) {
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case 0: colour_symbol->encoded_data[i][j] = '0'; break; /* white */
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case 1: colour_symbol->encoded_data[i][j] = 'Y'; break; /* yellow */
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case 2: colour_symbol->encoded_data[i][j] = 'M'; break; /* magenta */
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case 3: colour_symbol->encoded_data[i][j] = 'R'; break; /* red */
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case 4: colour_symbol->encoded_data[i][j] = 'C'; break; /* cyan */
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case 5: colour_symbol->encoded_data[i][j] = 'G'; break; /* green */
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case 6: colour_symbol->encoded_data[i][j] = 'B'; break; /* blue */
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case 7: colour_symbol->encoded_data[i][j] = '1'; break; /* black */
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}
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printf("%c",colour_symbol->encoded_data[i][j]);
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}
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printf("\n");
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}
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ZBarcode_Delete(red_symbol);
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ZBarcode_Delete(green_symbol);
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ZBarcode_Delete(blue_symbol);
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ZBarcode_Delete(colour_symbol);
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return 0;
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}</PRE><P>
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<HR>
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<TABLE WIDTH=100% BORDER=0 CELLPADDING=0 CELLSPACING=0>
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<TR VALIGN=TOP>
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<TD WIDTH=33% HEIGHT=5>
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<P ALIGN=LEFT><A HREF="appxc.html">Prev</A></P>
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</TD>
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<TD WIDTH=34%>
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<P ALIGN=CENTER><A HREF="index.html">Home</A></P>
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</TD>
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<TD WIDTH=33%>
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</TD>
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</TR>
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<TR VALIGN=TOP>
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<TD WIDTH=33%>
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<P ALIGN=LEFT>Appendix C</P>
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</TD>
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<TD WIDTH=34%>
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<P ALIGN=CENTER> </P>
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</TD>
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<TD WIDTH=33%>
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</TD>
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</TR>
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</TABLE>
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</BODY>
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</HTML>
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