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

[Michael Tremer <michael.tremer@ipfire.org>]

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Hello Leo,

> On 5 Aug 2021, at 10:40, Leo Hofmann <hofmann(a)leo-andres.de> wrote:
> 
> 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)

Okay. That seems to be a good improvement then. Around 10%. Cool.

-Michael

> 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
>>>