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

[Leo Hofmann <hofmann@leo-andres.de>]

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I used the Firefox developer tools to check the loading times of the images.

On average, the SVG image is generated 10ms faster: "HTTP Wait" for PNG: ~126ms, for SVG: ~115ms
(My test system: Core 159 on Proxmox VM/Xeon 3,3GHz)

Regards,
Leo

Am 04.08.2021 um 16:40 schrieb Michael Tremer:
> Cool. Thank you.
>
> Did you test if the SVG files can be generated quicker than PNG?
>
> -Michael
>
>> On 4 Aug 2021, at 13:01, Leo-Andres Hofmann <hofmann(a)leo-andres.de> wrote:
>>
>> 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
>> +;
>> }
>> -- 
>> 2.27.0.windows.1
>>