Added pixel limit detected by experimental tests

README.md

@@ -213,7 +213,7 @@ plugin ('n/a' means no limit, i.e. the limit depends on the format encoding).
 - EPS: n/a
 - HDR: n/a (large image)
 - HEIF: n/a
-- JP2: 300,000 x 300,000 pixels
+- JP2: 300,000 x 300,000 pixels, in any case no larger than 2 gigapixels
 - JXL: 262,144 x 262,144 pixels, in any case no larger than 256 megapixels
 - JXR: n/a, in any case no larger than 4 GB
 - KRA: same size as Qt's PNG plugin

src/imageformats/jp2.cpp

@@ -27,6 +27,13 @@
 #define JP2_MAX_IMAGE_HEIGHT JP2_MAX_IMAGE_WIDTH
 #endif
 
+/* *** JP2_MAX_IMAGE_PIXELS ***
+ * OpenJPEG seems limited to an image of 2 gigapixel size.
+ */
+#ifndef JP2_MAX_IMAGE_PIXELS
+#define JP2_MAX_IMAGE_PIXELS std::numeric_limits<qint32>::max()
+#endif
+
 /* *** JP2_ENABLE_HDR ***
  * Enable float image formats. Disabled by default
  * due to lack of test images.
@@ -332,6 +339,11 @@ public:
             return false;
         }
 
+        if (qint64(width) * qint64(height) > JP2_MAX_IMAGE_PIXELS) {
+            qCritical() << "Maximum image size is limited to" << JP2_MAX_IMAGE_PIXELS << "pixels";
+            return false;
+        }
+
         // OpenJPEG uses a shadow copy @32-bit/channel so we need to do a check
         auto maxBytes = qint64(QImageReader::allocationLimit()) * 1024 * 1024;
         auto neededBytes = qint64(width) * height * nchannels * 4;