If you have GD this will work for 24-bit color jpgs:

#! perl -slw
use strict;
use GD;

my $img = GD::Image->newFromJpeg( $ARGV[ 0 ], 1 )
    or die "$ARGV[ 0 ] : $!";

my( $width, $height ) = $img->getBounds();

( my $bmpFile = $ARGV[ 0 ] ) =~ s[.jpg$][.bmp]i;
open BMP, '>:raw', $bmpFile or die "$bmpFile : $!";
binmode BMP;

printf BMP '%s', pack 'A2ISSI', 'BM', $width * $height +54, 0, 0, 54;

printf BMP '%s', pack 'IiiSSIIiiII',
    40, $width, $height, 1, 24, 0, $width * $height, 11811, 11811, 0, 
+0;

for my $y ( reverse 0 .. $height-1 ) {
    for my $x ( 0 .. $width-1 ) {
        printf BMP '%s', pack 'CCC', reverse $img->rgb( $img->getPixel
+( $x, $y ) );
    }
}
close BMP;
[download]

Other color depths take a little more effort and it could be sped up quite easily.

Why isn't this a member function of GD::Image?

-Paul

Probably because the underlying GD Library doesn't have support for Windows .BMPs.

And that's probably because there is no existing open C library available for load/saving .BMPs as there are for .jpgs, .gifs etc.

And that maybe, though I haven't checked, because MS have never freely published the spcs for .BMPs?

Although my snippet works, for simple, uncompressed BMPs, the references I've seen suggest that 'the spec' has a multitude of extensions.

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

Why does this only work with 400x300pix images?
I have a 600x240 image. The bmp will be created, but i can't look at it nor use it.
Do i have to change some of these lines to work correctly?

There are no size limitations with the code. I just ran it on the biggest .jpg I had kicking around and it ran fine. Slow, but fine:

c:\test\img\tmp>imageinfo --verbose worldx2-2.jpg
worldx2-2.jpg
        File format: JPEG
        MIME type: image/jpeg
        Width (pixels): 5400
        Height (pixels): 2700
        Bits per pixel: 24
        Number of images: 1
        Physical width (dpi): 72
        Physical height (dpi): 72
        Physical width (inches): 75
        Physical height (inches): 37.500000
        Number of textual comments: 0

c:\test\img\tmp>..\..\Jpg2bmp.pl worldx2-2.jpg

c:\test\img\tmp>imageinfo --verbose worldx2-2.bmp
worldx2-2.bmp
        File format: BMP
        MIME type: image/bmp
        Width (pixels): 5400
        Height (pixels): 2700
        Bits per pixel: 24
        Number of images: 1
        Physical width (dpi): 300
        Physical height (dpi): 300
        Physical width (inches): 18
        Physical height (inches): 9
        Number of textual comments: 0
[download]

However, as noted above, it does only work for 24-bit images! I've updated the node with a slightly modified version that will abort if the image is not 24-bit.

It could be modified to handle palette images but it is a fair amount of work and there are far better (faster & more comprehensive) tools out there for performing image conversions.

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

ImageMagick is available for Windows. Instructions for installing PerlMagick on Windows.

Update: Bribes.org has a PPM repository that contains a PPD for ImageMagick.

Thank You for all answers. I installed the Image::Magick ppm from the Bribes PPM repository and it worked perfectly.

For future seekers of knowledge, the address of the repository is:
http://www.bribes.org/perl/ppm
Some useful repositories per CPAN
http://cpan.uwinnipeg.ca/htdocs/faqs/ppm.html


• http://crazyinsomniac.perlmonk.org/perl/ppm, for the crazyinsomniac Perl 5.6 repository
• http://crazyinsomniac.perlmonk.org/perl/ppm/5.8, for the crazyinsomniac Perl 5.8 repository
• http://www.bribes.org/perl/ppm, for the www.bribes.org Perl 5.6 and 5.8 repository
• http://theoryx5.uwinnipeg.ca/cgi-bin/ppmserver?urn:/PPMServer, for the uwinnipeg Perl 5.6 repository
• http://theoryx5.uwinnipeg.ca/cgi-bin/ppmserver?urn:/PPMServer58, for the uwinnipeg Perl 5.8 repository
For a nice place to live in Portland, OR

use Image::Magick;
my($image, $x);
$image = Image::Magick->new;
$x = $image->Read('test.jpg');
    warn "$x" if "$x";

$x = $image->Write('test.bmp');
    warn "$x" if "$x";
[download]

ppm> s ImageMagick
Searching in Active Repositories
  1. Apache-ImageMagick [2.0b7] Convert and manipulate images on the f
+ly
  2. Apache-ImageMagick [2.0b7] Convert and manipulate images on the f
+ly
ppm>
[download]