Nextcloud does not have support for generating thumbnails from Affinity Photo and Affinity Design. Fine, I'll do it myself.

Digging Binary

Glancing at .afphoto and .afdesign in Finder, I noticed that it has a QuickLook support and an ability to show the thumbnail image. So these files should have thumbnail image somewhere inside its binary.

I wrote a piece of Node.js script to seek for PNG signature inside a binary and save it as an image file.

afthumb.js
const fs = require("fs"); // png spec: https://www.w3.org/TR/PNG/ const PNG_SIG = Buffer.from([137, 80, 78, 71, 13, 10, 26, 10]); const IEND_SIG = Buffer.from([73, 69, 78, 68]); function extractThumbnail(buf) { const start = buf.indexOf(PNG_SIG); const end = buf.indexOf(IEND_SIG, start) + IEND_SIG.length * 2; // IEND + CRC return buf.subarray(start, end); } function generateThumbnail(input, output) { const buf = fs.readFileSync(input); const thumbBuf = extractThumbnail(buf); fs.writeFileSync(output, thumbBuf); } generateThumbnail(process.argv[2], process.argv[3] || "output.png");

That's right. This script just scrapes a binary file and distill a portion of which starts with PNG signature and ends with IEND.

Now I can generate a thumbnail image from arbitrary .afphoto and .afdesign file. Let's move on delving into Nextcloud source code.

Tweaking Nextcloud

I have a bit of experience in tweaking Nextcloud source code before, where I implemented thumbnail generator for PDFs, so it should be easier this time, hopefully.

Long story short, I got Nextcloud generates thumbnail images for Affinity files by implementing ProviderV2 class.

lib/private/Preview/Affinity.php
<?php namespace OC\Preview; use OCP\Files\File; use OCP\IImage; use OCP\ILogger; class Affinity extends ProviderV2 { public function getMimeType(): string { return '/application\/x-affinity-(?:photo|design)/'; } public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage { $tmpPath = $this->getLocalFile($file); $handle = fopen($tmpPath, 'rb'); $fsize = filesize($tmpPath); $contents = fread($handle, $fsize); $start = strrpos($contents, "\x89PNG"); $end = strrpos($contents, "IEND", $start); $subarr = substr($contents, $start, $end - $start + 8 ); fclose($handle); $this->cleanTmpFiles(); $image = new \OC_Image(); $image->loadFromData($subarr); $image->scaleDownToFit($maxX, $maxY); return $image->valid() ? $image : null; } }
lib/private/PreviewManager.php
@@ -363,6 +365,8 @@ $this->registerCoreProvider(Preview\Krita::class, '/application\/x-krita/'); $this->registerCoreProvider(Preview\MP3::class, '/audio\/mpeg/'); $this->registerCoreProvider(Preview\OpenDocument::class, '/application\/vnd.oasis.opendocument.*/'); + $this->registerCoreProvider(Preview\Affinity::class, '/application\/x-affinity-(?:photo|design)/'); // SVG, Office and Bitmap require imagick if (extension_loaded('imagick')) {
lib/composer/composer/autoload_static.php
@@ -1226,6 +1226,7 @@ 'OC\\OCS\\Result' => __DIR__ . '/../../..' . '/lib/private/OCS/Result.php', 'OC\\PreviewManager' => __DIR__ . '/../../..' . '/lib/private/PreviewManager.php', 'OC\\PreviewNotAvailableException' => __DIR__ . '/../../..' . '/lib/private/PreviewNotAvailableException.php', + 'OC\\Preview\\Affinity' => __DIR__ . '/../../..' . '/lib/private/Preview/Affinity.php', 'OC\\Preview\\BMP' => __DIR__ . '/../../..' . '/lib/private/Preview/BMP.php', 'OC\\Preview\\BackgroundCleanupJob' => __DIR__ . '/../../..' . '/lib/private/Preview/BackgroundCleanupJob.php', 'OC\\Preview\\Bitmap' => __DIR__ . '/../../..' . '/lib/private/Preview/Bitmap.php',
lib/composer/composer/autoload_classmap.php
@@ -1197,6 +1197,7 @@ 'OC\\OCS\\Result' => $baseDir . '/lib/private/OCS/Result.php', 'OC\\PreviewManager' => $baseDir . '/lib/private/PreviewManager.php', 'OC\\PreviewNotAvailableException' => $baseDir . '/lib/private/PreviewNotAvailableException.php', + 'OC\\Preview\\Affinity' => $baseDir . '/lib/private/Preview/Affinity.php', 'OC\\Preview\\BMP' => $baseDir . '/lib/private/Preview/BMP.php', 'OC\\Preview\\BackgroundCleanupJob' => $baseDir . '/lib/private/Preview/BackgroundCleanupJob.php', 'OC\\Preview\\Bitmap' => $baseDir . '/lib/private/Preview/Bitmap.php',

Easy-peasy!

Bonus: PDF thumbnail generator

Install ghostscript on your server to make it work.

lib/private/Preview/PDF.php
<?php namespace OC\Preview; use OCP\Files\File; use OCP\IImage; class PDF extends ProviderV2 { public function getMimeType(): string { return '/application\/pdf/'; } public function getThumbnail(File $file, int $maxX, int $maxY): ?IImage { $tmpPath = $this->getLocalFile($file); $outputPath = \OC::$server->getTempManager()->getTemporaryFile(); $gsBin = \OC_Helper::findBinaryPath('gs'); $cmd = $gsBin . " -o " . escapeshellarg($outputPath) . " -sDEVICE=jpeg -sPAPERSIZE=a4 -dLastPage=1 -dPDFFitPage -dJPEGQ=90 -r144 " . escapeshellarg($tmpPath); shell_exec($cmd); $this->cleanTmpFiles(); $image = new \OC_Image(); $image->loadFromFile($outputPath); $image->scaleDownToFit($maxX, $maxY); unlink($outputPath); return $image->valid() ? $image : null; } }