10 files changed, 36 insertions, 31 deletions
diff --git a/src/plugins/imageformats/icns/main.cpp b/src/plugins/imageformats/icns/main.cpp
index 70dd034..6a5af47 100644
--- a/src/plugins/imageformats/icns/main.cpp
+++ b/src/plugins/imageformats/icns/main.cpp
@@ -60,12 +60,12 @@ QImageIOPlugin::Capabilities QICNSPlugin::capabilities(QIODevice *device, const
 {
     if (format == QByteArrayLiteral("icns"))
         return Capabilities(CanRead | CanWrite);
+    Capabilities cap;
     if (!format.isEmpty())
-        return 0;
+        return cap;
     if (!device || !device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (device->isReadable() && QICNSHandler::canRead(device))
         cap |= CanRead;
     if (device->isWritable())
diff --git a/src/plugins/imageformats/jp2/main.cpp b/src/plugins/imageformats/jp2/main.cpp
index a1f1281..22368a5 100644
--- a/src/plugins/imageformats/jp2/main.cpp
+++ b/src/plugins/imageformats/jp2/main.cpp
@@ -64,12 +64,12 @@ QImageIOPlugin::Capabilities QJp2Plugin::capabilities(QIODevice *device, const Q
 {
     if (format == "jp2" || format == "j2k")
         return Capabilities(CanRead | CanWrite);
+    Capabilities cap;
     if (!format.isEmpty())
-        return 0;
+        return cap;
     if (!device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (device->isReadable() && QJp2Handler::canRead(device, 0))
         cap |= CanRead;
     if (device->isWritable())
diff --git a/src/plugins/imageformats/macheif/main.cpp b/src/plugins/imageformats/macheif/main.cpp
index 12d9a4a..785ad1f 100644
--- a/src/plugins/imageformats/macheif/main.cpp
+++ b/src/plugins/imageformats/macheif/main.cpp
@@ -58,16 +58,16 @@ QImageIOPlugin::Capabilities QMacHeifPlugin::capabilities(QIODevice *device, con
 {
     static const Capabilities sysCaps = QIIOFHelpers::systemCapabilities(QStringLiteral("public.heic"));
 
+    Capabilities cap;
     if (!sysCaps)
-        return 0;
+        return cap;
     if (format == "heic" || format == "heif")
         return sysCaps;
     if (!format.isEmpty())
-        return 0;
+        return cap;
     if (!device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (sysCaps.testFlag(CanRead) && device->isReadable() && QMacHeifHandler::canRead(device))
         cap |= CanRead;
     if (sysCaps.testFlag(CanWrite) && device->isWritable())
diff --git a/src/plugins/imageformats/macjp2/main.cpp b/src/plugins/imageformats/macjp2/main.cpp
index 08b497e..ea0cf44 100644
--- a/src/plugins/imageformats/macjp2/main.cpp
+++ b/src/plugins/imageformats/macjp2/main.cpp
@@ -57,12 +57,12 @@ QImageIOPlugin::Capabilities QMacJp2Plugin::capabilities(QIODevice *device, cons
 {
     if (format == "jp2")
         return Capabilities(CanRead | CanWrite);
+    Capabilities cap;
     if (!format.isEmpty())
-        return 0;
+        return cap;
     if (!device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (device->isReadable() && QMacJp2Handler::canRead(device))
         cap |= CanRead;
     if (device->isWritable())
diff --git a/src/plugins/imageformats/mng/main.cpp b/src/plugins/imageformats/mng/main.cpp
index 5e5b0a3..be82312 100644
--- a/src/plugins/imageformats/mng/main.cpp
+++ b/src/plugins/imageformats/mng/main.cpp
@@ -66,12 +66,12 @@ QImageIOPlugin::Capabilities QMngPlugin::capabilities(QIODevice *device, const Q
 {
     if (format == "mng")
         return Capabilities(CanRead);
+    Capabilities cap;
     if (!format.isEmpty())
-        return 0;
+        return cap;
     if (!device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (device->isReadable() && QMngHandler::canRead(device))
         cap |= CanRead;
     return cap;
diff --git a/src/plugins/imageformats/tga/main.cpp b/src/plugins/imageformats/tga/main.cpp
index 22fd3be..9177aa8 100644
--- a/src/plugins/imageformats/tga/main.cpp
+++ b/src/plugins/imageformats/tga/main.cpp
@@ -64,12 +64,12 @@ QImageIOPlugin::Capabilities QTgaPlugin::capabilities(QIODevice *device, const Q
 {
     if (format == "tga")
         return Capabilities(CanRead);
+    Capabilities cap;
     if (!format.isEmpty())
-        return 0;
+        return cap;
     if (!device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (device->isReadable() && QTgaHandler::canRead(device))
         cap |= CanRead;
     return cap;
diff --git a/src/plugins/imageformats/tiff/main.cpp b/src/plugins/imageformats/tiff/main.cpp
index 2c34097..8882f35 100644
--- a/src/plugins/imageformats/tiff/main.cpp
+++ b/src/plugins/imageformats/tiff/main.cpp
@@ -60,12 +60,12 @@ QImageIOPlugin::Capabilities QTiffPlugin::capabilities(QIODevice *device, const
 {
     if (format == "tiff" || format == "tif")
         return Capabilities(CanRead | CanWrite);
+    Capabilities cap;
     if (!format.isEmpty())
-        return 0;
+        return cap;
     if (!device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (device->isReadable() && QTiffHandler::canRead(device))
         cap |= CanRead;
     if (device->isWritable())
diff --git a/src/plugins/imageformats/tiff/qtiffhandler.cpp b/src/plugins/imageformats/tiff/qtiffhandler.cpp
index 65873e1..ad4e393 100644
--- a/src/plugins/imageformats/tiff/qtiffhandler.cpp
+++ b/src/plugins/imageformats/tiff/qtiffhandler.cpp
@@ -205,9 +205,14 @@ bool QTiffHandlerPrivate::canRead(QIODevice *device)
 
     // current implementation uses TIFFClientOpen which needs to be
     // able to seek, so sequential devices are not supported
-    QByteArray header = device->peek(4);
-    return header == QByteArray::fromRawData("\x49\x49\x2A\x00", 4)
-           || header == QByteArray::fromRawData("\x4D\x4D\x00\x2A", 4);
+    char h[4];
+    if (device->peek(h, 4) != 4)
+        return false;
+    if ((h[0] == 0x49 && h[1] == 0x49) && (h[2] == 0x2a || h[2] == 0x2b) && h[3] == 0)
+        return true; // Little endian, classic or bigtiff
+    if ((h[0] == 0x4d && h[1] == 0x4d) && h[2] == 0 && (h[3] == 0x2a || h[3] == 0x2b))
+        return true; // Big endian, classic or bigtiff
+    return false;
 }
 
 bool QTiffHandlerPrivate::openForRead(QIODevice *device)
diff --git a/src/plugins/imageformats/wbmp/main.cpp b/src/plugins/imageformats/wbmp/main.cpp
index 45da0ca..5e8206e 100644
--- a/src/plugins/imageformats/wbmp/main.cpp
+++ b/src/plugins/imageformats/wbmp/main.cpp
@@ -64,13 +64,13 @@ QImageIOPlugin::Capabilities QWbmpPlugin::capabilities(QIODevice *device, const
     if (format == "wbmp")
         return Capabilities(CanRead | CanWrite);
 
+    Capabilities cap;
     if (!format.isEmpty())
-        return 0;
+        return cap;
 
     if (!device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (device->isReadable() && QWbmpHandler::canRead(device))
         cap |= CanRead;
 
diff --git a/src/plugins/imageformats/webp/main.cpp b/src/plugins/imageformats/webp/main.cpp
index 7e9405b..02a3ed4 100644
--- a/src/plugins/imageformats/webp/main.cpp
+++ b/src/plugins/imageformats/webp/main.cpp
@@ -64,12 +64,12 @@ QWebpPlugin::Capabilities QWebpPlugin::capabilities(QIODevice *device, const QBy
     if (format == "webp")
         return Capabilities(CanRead | CanWrite);
 
+    Capabilities cap;
     if (!format.isEmpty())
-        return 0;
+        return cap;
     if (!device->isOpen())
-        return 0;
+        return cap;
 
-    Capabilities cap;
     if (device->isReadable() && QWebpHandler::canRead(device))
         cap |= CanRead;
     if (device->isWritable())