PNG is better if there is written text, JPG is better for drawings and images. The best converter is ImageMagick.

# using the ImageMagick c program
system( "convert  my.bmp my png");
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or using the Perl module, here is a generic conversion routine:

#!/usr/bin/perl
use warnings;
use strict;
use Image::Magick;

my $imgfile = shift;  # your BMP file

my $image = Image::Magick->new();
$image->Read($imgfile);
my $blob = $image->ImageToBlob(); # make in memory image

#and to convert
my $output = Image::Magick->new(magick=>'jpg');  # set your output for
+mat
$output->BlobToImage( $blob );
$output->Resize(geometry=>'160x120');
$output->Write( "$0.jpg" );

#or if you want to write to stdout
#binmode STDOUT;
#$output->Write('jpg:-');
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