Change only ImageIO decoded CGImage should enter the `Force Decode` logic

Others coder, like WebP, should not use this approach

SDWebImage/Core/UIImage+ForceDecode.m

@@ -14,7 +14,24 @@
 
 - (BOOL)sd_isDecoded {
     NSNumber *value = objc_getAssociatedObject(self, @selector(sd_isDecoded));
-    return value.boolValue;
+    if (value) {
+        return value.boolValue;
+    } else {
+        // Assume only CGImage based can use lazy decoding
+        CGImageRef cgImage = self.CGImage;
+        if (cgImage) {
+            CFStringRef uttype = CGImageGetUTType(self.CGImage);
+            if (uttype) {
+                // Only ImageIO can set `com.apple.ImageIO.imageSourceTypeIdentifier`
+                return NO;
+            } else {
+                // Thumbnail or CGBitmapContext drawn image
+                return YES;
+            }
+        }
+    }
+    // Assume others as non-decoded
+    return NO;
 }
 
 - (void)setSd_isDecoded:(BOOL)sd_isDecoded {

SDWebImage/Core/UIImage+Metadata.m

@@ -166,10 +166,8 @@
         return imageFormat;
     }
     // Check CGImage's UTType, may return nil for non-Image/IO based image
-    if (@available(iOS 9.0, tvOS 9.0, macOS 10.11, watchOS 2.0, *)) {
-        CFStringRef uttype = CGImageGetUTType(self.CGImage);
-        imageFormat = [NSData sd_imageFormatFromUTType:uttype];
-    }
+    CFStringRef uttype = CGImageGetUTType(self.CGImage);
+    imageFormat = [NSData sd_imageFormatFromUTType:uttype];
     return imageFormat;
 }