svg-png24-8.pl

#!/usr/bin/perl

# Perl Script to convert SVG images including PNG24 encoded images to SVG with PNG8 while retaining transparency

# Requirements:
# sudo cpan Image::Magick

use strict;
use warnings;
use Image::Magick;
use MIME::Base64 qw< encode_base64 decode_base64 >;

# Usage
# [sudo] perl svg-png24-8.pl input.svg

# Function to convert PNG24 to PNG8 
sub process_image {
    my ($png24_base64) = @_;
    
    #print "INPUT: " . substr($png24_base64,0,128) . "…\n\n";    
    my $image = Image::Magick->new;
    my $decoded = MIME::Base64::decode_base64($png24_base64);
		$image->Read(blob => $decoded);

    # Set image format to PNG8
    $image->Set(magick => 'PNG8');
    
    # Convert image to RGB?
    # $image->Quantize(colorspace => 'RGB');
    # print $image->Identify;

    # Get the resulting PNG8 image as binary blob
    my $png8_blob = $image->ImageToBlob();
    #print "png8_blob: " . substr($png8_blob,0,128) . "…\n\n";  
     
    # Encode the PNG8 blob as base64
    my $png8_base64 = encode_base64($png8_blob);
    #print "png8_base64: " . substr($png8_base64,0,128) . "…\n\n";  
 
		return $png8_base64;
}



# Check if a file name argument is provided
if (@ARGV != 1) {
    die "Usage: perl svg-png24-8.pl <input_file>\n";
}

# Input file name
my $input_file = $ARGV[0];

# Output file name with "-png8" appended
my $output_file = $input_file;
$output_file =~ s/(\.[^.]+)?$/-png8$1/;

# Regular expression pattern to match the desired strings
my $pattern = qr/"data:img\/png;base64,([^"]*)"/;

# Read input file
open my $input_fh, '<', $input_file or die "Failed to open input file: $!";

# Process the file line by line
my $output = "";
while (my $line = <$input_fh>) {
    chomp $line;
    
    # Check if the line matches the pattern
    if ($line =~ $pattern) {
    
				#print "\n\nLINE: " . substr($line,0,128);
    
        # Replace matched strings with processed result
        my $replacement = eval "process_image(\$1)";
        if ($@) {
            warn "Error during evaluation: $@";
            $replacement = $1;  # Use original string as replacement in case of error
        }
        
        # reintroduce header and quotes
				$replacement = '"data:image/png;base64,' . $replacement . '"';
        
        $line =~ s/$pattern/$replacement/;
        
    }

    $output .= $line . "\n";
}

# Close input file
close($input_fh);

# Save the modified content to the output file
open(my $output_fh, ">", $output_file) or die "Cannot open output file: $!";
print $output_fh $output;
close($output_fh);