Re: [PATCH] rrd graphs: Switch to SVG output format

[Bernhard Bitsch <bbitsch@ipfire.org>]

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No problems found at a quick test with Firefox.
Did not check errors, yet.

Reviewed-by: Bernhard Bitsch <bbitsch(a)ipfire.org>
Tested-by: Bernhard Bitsch <bbitsch(a)ipfire.org>


Am 04.08.2021 um 13:01 schrieb Leo-Andres Hofmann:
> The vector graphics can be scaled without becoming blurred.
> 
> Signed-off-by: Leo-Andres Hofmann <hofmann(a)leo-andres.de>
> ---
> 
> Hi,
> 
> Michael suggested switching to the SVG format for the graphs:
> https://lists.ipfire.org/pipermail/development/2021-July/010804.html
> 
> I have tested this with firefox and chrome, the graphs and error message look fine to me.
> If someone knows a good SVG validator, I would be happy to get the link :)
> 
> Regards,
> Leo
> 
>   config/cfgroot/graphs.pl     |  2 +-
>   html/cgi-bin/getrrdimage.cgi | 87 +++++++++++++++++++++---------------
>   2 files changed, 52 insertions(+), 37 deletions(-)
> 
> diff --git a/config/cfgroot/graphs.pl b/config/cfgroot/graphs.pl
> index 441d4c483..02341eb45 100644
> --- a/config/cfgroot/graphs.pl
> +++ b/config/cfgroot/graphs.pl
> @@ -40,7 +40,7 @@ my $ERROR;
>   
>   my @GRAPH_ARGS = (
>   	# Output format
> -	"--imgformat", "PNG",
> +	"--imgformat", "SVG",
>   
>   	# No border
>   	"--border", "0",
> diff --git a/html/cgi-bin/getrrdimage.cgi b/html/cgi-bin/getrrdimage.cgi
> index c08247c57..92f8b585d 100644
> --- a/html/cgi-bin/getrrdimage.cgi
> +++ b/html/cgi-bin/getrrdimage.cgi
> @@ -21,8 +21,7 @@
>   
>   use strict;
>   use URI;
> -use GD;
> -use GD::Text::Wrap;
> +use Text::Wrap;
>   use experimental 'smartmatch';
>   
>   # debugging
> @@ -52,7 +51,7 @@ my $range = lc $query{'range'}; # lower case
>   # Check parameters
>   unless(($origin =~ /^\w+?\.cgi$/) && ($graph =~ /^[\w\-.,; ]+?$/) && ($range ~~ @Graphs::time_ranges)) {
>   	# Send HTTP headers
> -	_start_png_output();
> +	_start_svg_output();
>   	
>   	_print_error("URL parameters missing or malformed.");	
>   	exit;
> @@ -76,7 +75,7 @@ unless(($origin ~~ @supported_origins) || ($origin eq "getrrdimage.cgi")) {
>   
>   ### Create graphs ###
>   # Send HTTP headers
> -_start_png_output();
> +_start_svg_output();
>   
>   # Graphs are first grouped by their origin.
>   # This is because some graph categories require special parameter handling.
> @@ -204,46 +203,62 @@ if($graphstatus) {
>   
>   ###--- Internal functions ---###
>   
> -# Send HTTP headers and switch to binary output
> +# Send HTTP headers
>   # (don't print any non-image data to STDOUT afterwards)
> -sub _start_png_output {
> +sub _start_svg_output {
>   	print "Cache-Control: no-cache, no-store\n";
> -	print "Content-Type: image/png\n";
> +	print "Content-Type: image/svg+xml\n";
>   	print "\n"; # End of HTTP headers
> -	binmode(STDOUT);
>   }
>   
> -# Print error message to PNG output
> +# Print error message to SVG output
>   sub _print_error {
>   	my ($message) = @_;
> -	$message = "- Error -\n \n$message";
> -
> -	# Create new image with the same size as a graph
> -	my $img = GD::Image->new($Graphs::image_size{'width'}, $Graphs::image_size{'height'});
> -	$img->interlaced('true');
> -
> -	# Basic colors
> -	my $color_background = $img->colorAllocate(255, 255, 255);
> -	my $color_border = $img->colorAllocate(255, 0, 0);
> -	my $color_text = $img->colorAllocate(0, 0, 0);
>   
> -	# Background and border
> -	$img->setThickness(2);
> -	$img->filledRectangle(0, 0, $img->width, $img->height, $color_background);
> -	$img->rectangle(10, 10, $img->width - 10, $img->height - 10, $color_border);
> -	
> -	# Draw message with line-wrap
> -	my $textbox = GD::Text::Wrap->new($img,
> -		text => $message,
> -		width => ($img->width - 50),
> -		color => $color_text,
> -		align => 'center',
> -		line_space => 5,
> -		preserve_nl => 1
> +	# Prepare image options
> +	my %img = (
> +		'width' => $Graphs::image_size{'width'},
> +		'height' => $Graphs::image_size{'height'},
> +		'text_center' => int($Graphs::image_size{'width'} / 2),
> +		'line_height' => 20,
> +		'font_family' => "DejaVu Sans, Helvetica, sans-serif" # Matching the IPFire theme
>   	);
> -	$textbox->set_font(gdLargeFont);
> -	$textbox->draw(25, 25);
>   
> -	# Get PNG output
> -	print $img->png;
> +	# Line-wrap message to fit image (adjust to font width if necessary)
> +	local($Text::Wrap::columns) = int($img{'width'} / 10);
> +	$message = wrap('', '', $message);
> +
> +	# Create new image with fixed background and border
> +	print <<END
> +<?xml version="1.0" encoding="UTF-8"?>
> +<svg width="$img{'width'}px" height="$img{'height'}px" viewBox="0 0 $img{'width'} $img{'height'}" version="1.1" xmlns="http://www.w3.org/2000/svg">
> +	<!-- Background -->
> +	<rect width="100%" height="100%" fill="white"/>
> +	<rect width="100%" height="100%" fill="none" stroke="red" stroke-width="2" transform="scale(0.95)" transform-origin="center"/>
> +	<!-- Message -->
> +	<text x="$img{'text_center'}" y="50" font-size="20" font-family="$img{'font_family'}" text-anchor="middle">- $Lang::tr{'error'} -</text>
> +	<text x="$img{'text_center'}" y="90" font-size="14" font-family="$img{'font_family'}" text-anchor="middle">
> +END
> +;
> +
> +	# Print message lines
> +	my $shift_y = 0; # Shifts text along y-axis
> +	foreach my $line (split(/\n/, $message)) {
> +		if($line ne "") { # Don't create empty tspan elements
> +			print <<END
> +		<tspan x="$img{'text_center'}" dy="$shift_y">$line</tspan>
> +END
> +;
> +			$shift_y = $img{'line_height'};
> +		} else { # Create blank lines by summing up unused line height
> +			$shift_y += $img{'line_height'};
> +		}
> +	}
> +
> +	# Finish SVG output
> +	print <<END
> +	</text>
> +</svg>
> +END
> +;
>   }
>