Update the default force decode value, partial revert ff6b3b9bb5

Now it's will mark as false for not byte-aligned CGImage

SDWebImage/Core/UIImage+ForceDecode.h

@@ -15,6 +15,12 @@
 
 /**
  A bool value indicating whether the image has already been decoded. This can help to avoid extra force decode.
+ Force decode is used for 2 cases:
+ -- 1. for ImageIO created image (via `CGImageCreateWithImageSource` SPI), it's lazy and we trigger the decode before rendering
+ -- 2. for non-ImageIO created image (via `CGImageCreate` API), we can ensure it's alignment is suitable to render on screen without copy by CoreAnimation
+ @note For coder plugin developer, always use the SDImageCoderHelper's `colorSpaceGetDeviceRGB`/`preferredByteAlignment`/`preferredBitmapInfo:` to create CGImage.
+ @note For more information why force decode, see: https://github.com/path/FastImageCache#byte-alignment
+ @note The defaults value is calculated based on UIImage's CGImage status. Do not assume it's always work as expected. Set the value to `true` if you don't need force decode
  */
 @property (nonatomic, assign) BOOL sd_isDecoded;
 

SDWebImage/Core/UIImage+ForceDecode.m

@@ -20,19 +20,26 @@
     } else {
         // Assume only CGImage based can use lazy decoding
         CGImageRef cgImage = self.CGImage;
-        if (cgImage) {
+        if (!cgImage) {
-            CFStringRef uttype = CGImageGetUTType(self.CGImage);
+            // Assume others as non-decoded
-            if (uttype) {
+            return NO;
-                // Only ImageIO can set `com.apple.ImageIO.imageSourceTypeIdentifier`
+        }
-                return NO;
+        CFStringRef uttype = CGImageGetUTType(self.CGImage);
-            } else {
+        if (uttype) {
-                // Thumbnail or CGBitmapContext drawn image
+            // Only ImageIO can set `com.apple.ImageIO.imageSourceTypeIdentifier`
+            return NO;
+        } else {
+            // Now, let's check if the CGImage is byte-aligned (not aligned will cause extra copy)
+            size_t bytesPerRow = CGImageGetBytesPerRow(cgImage);
+            if (SDByteAlign(bytesPerRow, [SDImageCoderHelper preferredByteAlignment]) == bytesPerRow) {
+                // byte aligned, OK
                 return YES;
+            } else {
+                // not aligned, still need force-decode
+                return NO;
             }
         }
     }
-    // Assume others as non-decoded
-    return NO;
 }
 
 - (void)setSd_isDecoded:(BOOL)sd_isDecoded {