steves has asked for the wisdom of the Perl Monks concerning the following question:

I know something like this must exist, but I can't find it ... I'd like to find a good starting point for building a simple Perl CGI that displays a clickable image map of colors, then just builds a simple page using a selected color as the background color. Any pointers?

Replies are listed 'Best First'.
Re: color selection image map
by vladb (Vicar) on May 22, 2002 at 21:40 UTC
    CPAN is your friend, my friend! ;-).

    Let me suggest you use this module CGI::Imagemap to build your HTMLized image maps via a Perl CGI script. Refer to the module documentation for more info (I found it very clear and descriptive).

    Hope this helps! ;)

    _____________________ 
    $"=q;grep;;$,=q"grep";for(`find . -name ".saves*~"`){s;$/;;;/(.*-(\d+)
+-.*)$/;$_=&#91"ps -e -o pid | "," $2 | "," -v "," "]`@$_`?{print"
++ $1"}:{print"- $1"}&&`rm $1`;print"\n";}

    [download]
[reply]
[d/l]
Re: color selection image map
by mt2k (Hermit) on May 23, 2002 at 06:02 UTC
    Here is a modified version of a script I have used in the past for something like this. It offers users an option of what color to use for design features (such as background color, text color, links, etc.). The only REALLY ugly thing about this is that it is all in an HTML table... so the browser has to load the entire (quite lengthy) HTML file before it can display any of the color options. But I have found it isn't TOO bad. Though I myself might be changing over to an image map :) But have a crack at it anyway.

    For the example, I have provided, as the list, the "web-safe" color palette. These are the colors that are supposedly displayed the same on all monitors/browsers. As a rule of thumb, only colors from this list should be used when designing web sites on the internet :)

    #!c:/perl/bin/perl
use strict;
use CGI;

################################
#CONFIGURATION FOR SCRIPT      #
################################

# Please note that $cols * $rows MUST multiply to the
# same number of colors in the @colors array.
# If this rule is not followed, incorrect HTML
# will be outputted.

my $cols = 18; # Number of columns to display
my $rows = 12; # Number of rows to display

#Here is the list of all colors to be shown
my @colors = qw(
000000 000033 000066 000099 0000CC 0000FF 003300 003333 003366 003399 
+0033CC 0033FF 006600 006633 006666 006699 0066CC 0066FF
009900 009933 009966 009999 0099CC 0099FF 00CC00 00CC33 00CC66 00CC99 
+00CCCC 00CCFF 00FF00 00FF33 00FF66 00FF99 00FFCC 00FFFF
330000 330033 330066 330099 3300CC 3300FF 333300 333333 333366 333399 
+3333CC 3333FF 336600 336633 336666 336699 3366CC 3366FF
339900 339933 339966 339999 3399CC 3399FF 33CC00 33CC33 33CC66 33CC99 
+33CCCC 33CCFF 33FF00 33FF33 33FF66 33FF99 33FFCC 33FFFF
660000 660033 660066 660099 6600CC 6600FF 663300 663333 663366 663399 
+6633CC 6633FF 666600 666633 666666 666699 6666CC 6666FF
669900 669933 669966 669999 6699CC 6699FF 66CC00 66CC33 66CC66 66CC99 
+66CCCC 66CCFF 66FF00 66FF33 66FF66 66FF99 66FFCC 66FFFF
990000 990033 990066 990099 9900CC 9900FF 993300 993333 993366 993399 
+9933CC 9933FF 996600 996633 996666 996699 9966CC 9966FF
999900 999933 999966 999999 9999CC 9999FF 99CC00 99CC33 99CC66 99CC99 
+99CCCC 99CCFF 99FF00 99FF33 99FF66 99FF99 99FFCC 99FFFF
CC0000 CC0033 CC0066 CC0099 CC00CC CC00FF CC3300 CC3333 CC3366 CC3399 
+CC33CC CC33FF CC6600 CC6633 CC6666 CC6699 CC66CC CC66FF
CC9900 CC9933 CC9966 CC9999 CC99CC CC99FF CCCC00 CCCC33 CCCC66 CCCC99 
+CCCCCC CCCCFF CCFF00 CCFF33 CCFF66 CCFF99 CCFFCC CCFFFF
FF0000 FF0033 FF0066 FF0099 FF00CC FF00FF FF3300 FF3333 FF3366 FF3399 
+FF33CC FF33FF FF6600 FF6633 FF6666 FF6699 FF66CC FF66FF
FF9900 FF9933 FF9966 FF9999 FF99CC FF99FF FFCC00 FFCC33 FFCC66 FFCC99 
+FFCCCC FFCCFF FFFF00 FFFF33 FFFF66 FFFF99 FFFFCC FFFFFF
);


# Are colors in @colors in hex or name form?
# '1' for hex colors (like '#0F0F0F')
# '0' for named colors (like 'red')
my $colors_hex = 1;

###########################
#END CONFIGURATION        #
###########################

my $count;
my %input;
my $query = new CGI;
$input{$_} = $query->param($_) foreach ($query->param());

if (defined($input{'bg'})) {
    &print_it ("Your current background color is #$input{'bg'}. Select
+ a new color:");
} else {
    $input{'bg'} = "FFFFFF";
    &print_it ("Please select a color for your background:");
}

sub print_it {
my $bg;
if ($colors_hex == 1) { $bg = '#'; } else { $bg = ''; }

print qq|Content-type: text/html\n
<html>
<head>
<title>Select Color</title>
</head>

<body bgcolor="$bg$input{'bg'}">
$_[0]<p>

<table border="0" cellpadding="0" cellspacing="1">
|;

foreach (@colors) {
if ($count % $cols == 0 && $count != 0) { print qq|</tr>|; }
if ($count % $cols == 0 && $count != ($cols * $rows)) { print qq|<tr>|
+; }

print qq|
<td bgcolor="$bg$_" height="15" width="15" bgcolor="#$_">
<a href="$ENV{'SCRIPT_NAME'}?bg=$_"><font color="$bg$_">&nbsp;&nbsp;&n
+bsp;&nbsp;&nbsp;</font></a>
</td>
|;
$count++;

}

print qq|
</tr>
</table>
</body>
</html>
|;
}

    [download]
[reply]
[d/l]

      It turns out that ImageMagick makes this amazingly easy. They have a built in 'netscape' color cube image that just builds the grid. Here's the small chunk of code that does that: 

      use Image::Magick;  # I actually use a wrapper here to set the env.  
my $status;
my $image = Image::Magick->new();

$status = $image->Read("netscape:");
warn $status if ($status);
$status = $image->Scale('256x256+256');
warn $status if ($status);
$status = $image->Write('background.gif');
('map:../../htdocs/background.map');
warn $status if ($status);
$status = $image->Write('html:../../htdocs/background.html');
warn $status if ($status);

      [download]

      You can also create the associated map, but I just used standard Perl CGI to generate a page using the image I created and field the image map params coming back. It looks at the coordinates and again uses ImageMagick to query the image's color at the location, convert that to hex and show the page again.

      Here's the CGI code ... a little fugly but I can clean it up later, right? 8-) This may not work as is -- there was another proprietary piece I can really put out for public consumption. 

      #!/usr/local/bin/perl

use CGI qw/:standard/;
use Image::Magick;
use URI::Escape;

my $color;
my $hex_color = '#ffffff';
my $esc_color;
my $status;

sub hex_color
{
    my ($number, $hex);

    (shift @_) =~ /^(\d+),(\d+),(\d+)/;

    foreach $number ($1, $2, $3)
    {
        $hex .= sprintf("%02X", 0xff & $number);
    }

    return '#' . $hex;
}

if (param())
{
    if (defined(param('hex_text')))
    {
        $hex_color = param('hex_value');
        $hex_color = '#' . $hex_color if ($hex_color !~ /^\#/);
    }
    else
    {
        my ($x, $y) = (param('color.x'), param('color.y'));

        my $image = Image::Magick->new();
        $status = $image->read("../htdocs/background.gif");
        print STDERR "$status\n" if ($status);

        $color = $image->Get("pixel[$x, $y]");

        $hex_color = hex_color($color);
    }
}

$esc_color = uri_escape($hex_color);

my $instructions = <<"END_TEXT";
<P><I>Click the color map or enter a specific hex color in the text bo
+x.</I>
</P>
END_TEXT

print header,
      start_html({-bgcolor => substr($hex_color, 1)},
                 'Background Color Tester'),
      h1({-align => 'center'}, "Background Color Tester"),
      h2({-align => 'center'}, "Hex Color Value Is:  $hex_color"),
      h3({-align => 'center'}, $instructions),
      start_form(),
      table({-align => 'center'},
            Tr({-align => 'center'},
               td({-align => 'center'},
                  image_button(-name     => 'color',
                               -src      => '/background.gif',
                               -width    => 256,
                               -height   => 171,
                               -align    => 'MIDDLE',
                              ),
                 ),
              ),
           ),
      table({-align => 'center'},
            Tr({-align => 'center'},
               td({-align => 'center'},
                  textfield(-name => 'hex_value',
                            -size => 7,
                           ),
                 ),
               td({-align => 'center'},
                  submit   (-value => 'Hex Value',
                            -name  => 'hex_text',
                           ),
                 ),
              ),
            ),
      end_form(),
      end_html();

      [download]
[reply]
[d/l]
[select]

        I also implemented a version that's entirely client side image maps and JavaScript, which actually fits the need a little better. No Perl in that one, but I thought I'd mention it as a final follow-up. I know all the evils of JavaScript, but in this case it makes sense ...

[reply]
Re: color selection image map
by shotgunefx (Parson) on May 22, 2002 at 21:49 UTC
    You say nothing of how you want to select your colors.Do you want to select from a fixed MxN palette or abitrarily zoom in on a RGB color cube?

    -Lee

    "To be civilized is to deny one's nature."
[reply]
      Here's a rough idea for a zooming version that would let you select arbitrary colors using RGB.

      You'll need to use GD or Image magik to generate the images which will be 255x255. Well that or generate a raw image file which I don't recommend.

      Use the x axis for green and y for red. What I mean is that point 0,0 should be (Red,Green) = (0,0) Point 255,255 will be (Red,Green) = (255,255).

      By using an image type input, you will be able to dicern what value the user clicked by using the x,y as indexes. You've now got the red and green values.

      You will need a text input field for Blue which you can think of as the z axis of the cube. The only downside is generating the images. You could generate them and store them instead for speed as uncompressed it's only about a meg total.

      When the user changes the blue axis, you just use that as an index to the right image (Or generate it dynamically). Then you just take the x,y of the click and the blue index and you have your color. The plus side of the complexity is that you can select any RGB value possible.

      I may get around coding this myself (It's been on my list for awhile) but right now I don't have the time to put it together.

      Good luck

      -Lee

      "To be civilized is to deny one's nature."
[reply]

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