Adds more context to the svg compatibility warning

[pierreozoux]

Refers to this lengthy discussion:
nextcloud/docker#1414

[tcitworld]

Adding this part without extra context and this message still being a recommendation is really not useful. :/

Also, by default, Nextcloud uses Imagick with SVG support only to generate some themed icons, which is a far lower exposure surface than the rendering previews for SVG files (which is disabled by default for a good reason).

It seems than nextcloud/docker#1414 is quite confused by all this.

[TLATER]

Ah, interesting! Scrolling by because I was trying to add a similar message, I hadn't realized that imagemagick was used for separate purposes. Let's see if we can finally solve nextcloud/docker#1414 by adding imagemagick to the image instead then.

[mschoettle]

Interesting. If it is used to generate themed icons, is this happening all the time or only in certain cases (i.e., not mandatory)?

[tcitworld]

It's used for instance to generate avatars containing the user's initials, and fallbacks to the samething with the GD library if it fails (GD may produce ugly things).

server/lib/private/Avatar/PlaceholderAvatar.php

Lines 134 to 136 in 12ed5c9

	if (!$data = $this->generateAvatarFromSvg($size)) {
	$data = $this->generateAvatar($this->getDisplayName(), $size);
	}

Pretty much the same goes with themed favicons and app icons when the base logo is an svg.

server/apps/theming/lib/IconBuilder.php

Lines 120 to 223 in 12ed5c9

	/**
	* Render app icon on themed background color
	* fallback to logo
	*
	* @param $app string app name
	* @param $size int size of the icon in px
	* @return Imagick|false
	*/
	public function renderAppIcon($app, $size) {
	$appIcon = $this->util->getAppIcon($app);
	if ($appIcon === false) {
	return false;
	}
	if ($appIcon instanceof ISimpleFile) {
	$appIconContent = $appIcon->getContent();
	$mime = $appIcon->getMimeType();
	} else {
	$appIconContent = file_get_contents($appIcon);
	$mime = mime_content_type($appIcon);
	}
	if ($appIconContent === false || $appIconContent === "") {
	return false;
	}
	$color = $this->themingDefaults->getColorPrimary();
	// generate background image with rounded corners
	$background = '<?xml version="1.0" encoding="UTF-8"?>' .
	'<svg xmlns="http://www.w3.org/2000/svg" version="1.1" xmlns:cc="http://creativecommons.org/ns#" width="512" height="512" xmlns:xlink="http://www.w3.org/1999/xlink">' .
	'<rect x="0" y="0" rx="100" ry="100" width="512" height="512" style="fill:' . $color . ';" />' .
	'</svg>';
	// resize svg magic as this seems broken in Imagemagick
	if ($mime === "image/svg+xml" || substr($appIconContent, 0, 4) === "<svg") {
	if (substr($appIconContent, 0, 5) !== "<?xml") {
	$svg = "<?xml version=\"1.0\"?>".$appIconContent;
	} else {
	$svg = $appIconContent;
	}
	$tmp = new Imagick();
	$tmp->readImageBlob($svg);
	$x = $tmp->getImageWidth();
	$y = $tmp->getImageHeight();
	$res = $tmp->getImageResolution();
	$tmp->destroy();
	if ($x > $y) {
	$max = $x;
	} else {
	$max = $y;
	}
	// convert svg to resized image
	$appIconFile = new Imagick();
	$resX = (int)(512 * $res['x'] / $max * 2.53);
	$resY = (int)(512 * $res['y'] / $max * 2.53);
	$appIconFile->setResolution($resX, $resY);
	$appIconFile->setBackgroundColor(new ImagickPixel('transparent'));
	$appIconFile->readImageBlob($svg);
	/**
	* invert app icons for bright primary colors
	* the default nextcloud logo will not be inverted to black
	*/
	if ($this->util->invertTextColor($color)
	&& !$appIcon instanceof ISimpleFile
	&& $app !== "core"
	) {
	$appIconFile->negateImage(false);
	}
	$appIconFile->scaleImage(512, 512, true);
	} else {
	$appIconFile = new Imagick();
	$appIconFile->setBackgroundColor(new ImagickPixel('transparent'));
	$appIconFile->readImageBlob($appIconContent);
	$appIconFile->scaleImage(512, 512, true);
	}
	// offset for icon positioning
	$border_w = (int)($appIconFile->getImageWidth() * 0.05);
	$border_h = (int)($appIconFile->getImageHeight() * 0.05);
	$innerWidth = ($appIconFile->getImageWidth() - $border_w * 2);
	$innerHeight = ($appIconFile->getImageHeight() - $border_h * 2);
	$appIconFile->adaptiveResizeImage($innerWidth, $innerHeight);
	// center icon
	$offset_w = (int)(512 / 2 - $innerWidth / 2);
	$offset_h = (int)(512 / 2 - $innerHeight / 2);
	$finalIconFile = new Imagick();
	$finalIconFile->setBackgroundColor(new ImagickPixel('transparent'));
	$finalIconFile->readImageBlob($background);
	$finalIconFile->setImageVirtualPixelMethod(Imagick::VIRTUALPIXELMETHOD_TRANSPARENT);
	$finalIconFile->setImageArtifact('compose:args', "1,0,-0.5,0.5");
	$finalIconFile->compositeImage($appIconFile, Imagick::COMPOSITE_ATOP, $offset_w, $offset_h);
	$finalIconFile->setImageFormat('png24');
	if (defined("Imagick::INTERPOLATE_BICUBIC") === true) {
	$filter = Imagick::INTERPOLATE_BICUBIC;
	} else {
	$filter = Imagick::FILTER_LANCZOS;
	}
	$finalIconFile->resizeImage($size, $size, $filter, 1, false);
	$appIconFile->destroy();
	return $finalIconFile;
	}

So it's really as the message says, just better compatibility.