add a maximum RAM usage for images

src/messages/Image.cpp

@@ -405,6 +405,16 @@ void Image::actuallyLoad()
             QBuffer buffer(const_cast<QByteArray *>(&data));
             buffer.open(QIODevice::ReadOnly);
             QImageReader reader(&buffer);
+
+            if (reader.size().width() * reader.size().height() *
+                    reader.imageCount() * 4 >
+                Image::maxBytesRam)
+            {
+                qCDebug(chatterinoImage) << "image too large in RAM";
+
+                return Failure;
+            }
+
             auto parsed = detail::readFrames(reader, shared->url());
 
             postToThread(makeConvertCallback(parsed, [weak](auto frames) {

src/messages/Image.hpp

@@ -50,6 +50,9 @@ using ImagePtr = std::shared_ptr<Image>;
 class Image : public std::enable_shared_from_this<Image>, boost::noncopyable
 {
 public:
+    // Maximum amount of RAM used by the image in bytes.
+    static constexpr int maxBytesRam = 20 * 1024 * 1024;
+
     ~Image();
 
     static ImagePtr fromUrl(const Url &url, qreal scale = 1);