Bridge the exist options `SDWebImageScaleDownLargeImages`, to use the thumbnail decoding instead. Defaults use 60MB limit and thumbnail size is (3966, 3966)

SDWebImage/Core/SDImageCacheDefine.m

@@ -19,7 +19,16 @@ UIImage * _Nullable SDImageCacheDecodeImageData(NSData * _Nonnull imageData, NSS
     NSNumber *scaleValue = context[SDWebImageContextImageScaleFactor];
     CGFloat scale = scaleValue.doubleValue >= 1 ? scaleValue.doubleValue : SDImageScaleFactorForKey(cacheKey);
     NSNumber *preserveAspectRatioValue = context[SDWebImageContextImagePreserveAspectRatio];
-    NSValue *thumbnailSizeValue = context[SDWebImageContextImageThumbnailPixelSize];
+    NSValue *thumbnailSizeValue;
+    BOOL shouldScaleDown = SD_OPTIONS_CONTAINS(options, SDWebImageScaleDownLargeImages);
+    if (shouldScaleDown) {
+        CGFloat thumbnailPixels = SDImageCoderHelper.defaultScaleDownLimitBytes / 4;
+        CGFloat dimension = ceil(sqrt(thumbnailPixels));
+        thumbnailSizeValue = @(CGSizeMake(dimension, dimension));
+    }
+    if (context[SDWebImageContextImageThumbnailPixelSize]) {
+        thumbnailSizeValue = context[SDWebImageContextImageThumbnailPixelSize];
+    }
     
     SDImageCoderMutableOptions *mutableCoderOptions = [NSMutableDictionary dictionaryWithCapacity:2];
     mutableCoderOptions[SDImageCoderDecodeFirstFrameOnly] = @(decodeFirstFrame);

SDWebImage/Core/SDImageCoderHelper.h

@@ -90,6 +90,12 @@
 + (UIImage * _Nullable)decodedAndScaledDownImageWithImage:(UIImage * _Nullable)image limitBytes:(NSUInteger)bytes;
 
 #if SD_UIKIT || SD_WATCH
+/**
+ Control the default limit bytes to scale down larget images.
+ This value must be larger than or equal to 1MB. Defaults to 60MB.
+ */
+@property (class, readwrite) NSUInteger defaultScaleDownLimitBytes;
+
 /**
  Convert an EXIF image orientation to an iOS one.
 

SDWebImage/Core/SDImageCoderHelper.m

@@ -18,26 +18,15 @@
 static const size_t kBytesPerPixel = 4;
 static const size_t kBitsPerComponent = 8;
 
+static const CGFloat kBytesPerMB = 1024.0f * 1024.0f;
+static const CGFloat kPixelsPerMB = kBytesPerMB / kBytesPerPixel;
 /*
  * Defines the maximum size in MB of the decoded image when the flag `SDWebImageScaleDownLargeImages` is set
  * Suggested value for iPad1 and iPhone 3GS: 60.
  * Suggested value for iPad2 and iPhone 4: 120.
  * Suggested value for iPhone 3G and iPod 2 and earlier devices: 30.
  */
-static const CGFloat kDestImageSizeMB = 60.f;
+static CGFloat kDestImageLimitBytes = 60.f * kBytesPerMB;
-
-/*
- * Defines the maximum size in MB of a tile used to decode image when the flag `SDWebImageScaleDownLargeImages` is set
- * Suggested value for iPad1 and iPhone 3GS: 20.
- * Suggested value for iPad2 and iPhone 4: 40.
- * Suggested value for iPhone 3G and iPod 2 and earlier devices: 10.
- */
-static const CGFloat kSourceImageTileSizeMB = 20.f;
-
-static const CGFloat kBytesPerMB = 1024.0f * 1024.0f;
-static const CGFloat kPixelsPerMB = kBytesPerMB / kBytesPerPixel;
-static const CGFloat kDestTotalPixels = kDestImageSizeMB * kPixelsPerMB;
-static const CGFloat kTileTotalPixels = kSourceImageTileSizeMB * kPixelsPerMB;
 
 static const CGFloat kDestSeemOverlap = 2.0f;   // the numbers of pixels to overlap the seems where tiles meet.
 #endif
@@ -311,13 +300,11 @@ static const CGFloat kDestSeemOverlap = 2.0f;   // the numbers of pixels to over
     
     CGFloat destTotalPixels;
     CGFloat tileTotalPixels;
-    if (bytes > 0) {
+    if (bytes == 0) {
-        destTotalPixels = bytes / kBytesPerPixel;
+        bytes = kDestImageLimitBytes;
-        tileTotalPixels = destTotalPixels / 3;
-    } else {
-        destTotalPixels = kDestTotalPixels;
-        tileTotalPixels = kTileTotalPixels;
     }
+    destTotalPixels = bytes / kBytesPerPixel;
+    tileTotalPixels = destTotalPixels / 3;
     CGContextRef destContext;
     
     // autorelease the bitmap context and all vars to help system to free memory when there are memory warning.
@@ -433,6 +420,17 @@ static const CGFloat kDestSeemOverlap = 2.0f;   // the numbers of pixels to over
 }
 
 #if SD_UIKIT || SD_WATCH
++ (NSUInteger)defaultScaleDownLimitBytes {
+    return kDestImageLimitBytes;
+}
+
++ (void)setDefaultScaleDownLimitBytes:(NSUInteger)defaultScaleDownLimitBytes {
+    if (defaultScaleDownLimitBytes < kBytesPerMB) {
+        return;
+    }
+    kDestImageLimitBytes = defaultScaleDownLimitBytes;
+}
+
 // Convert an EXIF image orientation to an iOS one.
 + (UIImageOrientation)imageOrientationFromEXIFOrientation:(CGImagePropertyOrientation)exifOrientation {
     UIImageOrientation imageOrientation = UIImageOrientationUp;
@@ -533,11 +531,10 @@ static const CGFloat kDestSeemOverlap = 2.0f;   // the numbers of pixels to over
         return NO;
     }
     CGFloat destTotalPixels;
-    if (bytes > 0) {
+    if (bytes == 0) {
-        destTotalPixels = bytes / kBytesPerPixel;
+        bytes = kDestImageLimitBytes;
-    } else {
-        destTotalPixels = kDestTotalPixels;
     }
+    destTotalPixels = bytes / kBytesPerPixel;
     if (destTotalPixels <= kPixelsPerMB) {
         // Too small to scale down
         return NO;

SDWebImage/Core/SDImageLoader.m

@@ -33,7 +33,16 @@ UIImage * _Nullable SDImageLoaderDecodeImageData(NSData * _Nonnull imageData, NS
     NSNumber *scaleValue = context[SDWebImageContextImageScaleFactor];
     CGFloat scale = scaleValue.doubleValue >= 1 ? scaleValue.doubleValue : SDImageScaleFactorForKey(cacheKey);
     NSNumber *preserveAspectRatioValue = context[SDWebImageContextImagePreserveAspectRatio];
-    NSValue *thumbnailSizeValue = context[SDWebImageContextImageThumbnailPixelSize];
+    NSValue *thumbnailSizeValue;
+    BOOL shouldScaleDown = SD_OPTIONS_CONTAINS(options, SDWebImageScaleDownLargeImages);
+    if (shouldScaleDown) {
+        CGFloat thumbnailPixels = SDImageCoderHelper.defaultScaleDownLimitBytes / 4;
+        CGFloat dimension = ceil(sqrt(thumbnailPixels));
+        thumbnailSizeValue = @(CGSizeMake(dimension, dimension));
+    }
+    if (context[SDWebImageContextImageThumbnailPixelSize]) {
+        thumbnailSizeValue = context[SDWebImageContextImageThumbnailPixelSize];
+    }
     
     SDImageCoderMutableOptions *mutableCoderOptions = [NSMutableDictionary dictionaryWithCapacity:2];
     mutableCoderOptions[SDImageCoderDecodeFirstFrameOnly] = @(decodeFirstFrame);
@@ -75,12 +84,7 @@ UIImage * _Nullable SDImageLoaderDecodeImageData(NSData * _Nonnull imageData, NS
         }
         
         if (shouldDecode) {
-            BOOL shouldScaleDown = SD_OPTIONS_CONTAINS(options, SDWebImageScaleDownLargeImages);
+            image = [SDImageCoderHelper decodedImageWithImage:image];
-            if (shouldScaleDown) {
-                image = [SDImageCoderHelper decodedAndScaledDownImageWithImage:image limitBytes:0];
-            } else {
-                image = [SDImageCoderHelper decodedImageWithImage:image];
-            }
         }
     }
     
@@ -104,7 +108,16 @@ UIImage * _Nullable SDImageLoaderDecodeProgressiveImageData(NSData * _Nonnull im
     NSNumber *scaleValue = context[SDWebImageContextImageScaleFactor];
     CGFloat scale = scaleValue.doubleValue >= 1 ? scaleValue.doubleValue : SDImageScaleFactorForKey(cacheKey);
     NSNumber *preserveAspectRatioValue = context[SDWebImageContextImagePreserveAspectRatio];
-    NSValue *thumbnailSizeValue = context[SDWebImageContextImageThumbnailPixelSize];
+    NSValue *thumbnailSizeValue;
+    BOOL shouldScaleDown = SD_OPTIONS_CONTAINS(options, SDWebImageScaleDownLargeImages);
+    if (shouldScaleDown) {
+        CGFloat thumbnailPixels = SDImageCoderHelper.defaultScaleDownLimitBytes / 4;
+        CGFloat dimension = ceil(sqrt(thumbnailPixels));
+        thumbnailSizeValue = @(CGSizeMake(dimension, dimension));
+    }
+    if (context[SDWebImageContextImageThumbnailPixelSize]) {
+        thumbnailSizeValue = context[SDWebImageContextImageThumbnailPixelSize];
+    }
     
     SDImageCoderMutableOptions *mutableCoderOptions = [NSMutableDictionary dictionaryWithCapacity:2];
     mutableCoderOptions[SDImageCoderDecodeFirstFrameOnly] = @(decodeFirstFrame);

SDWebImage/Core/SDWebImageDefine.h

@@ -122,9 +122,12 @@ typedef NS_OPTIONS(NSUInteger, SDWebImageOptions) {
     SDWebImageAvoidAutoSetImage = 1 << 10,
     
     /**
-     * By default, images are decoded respecting their original size. On iOS, this flag will scale down the
+     * By default, images are decoded respecting their original size.
-     * images to a size compatible with the constrained memory of devices.
+     * On iOS/tvOS/watchOS, this flag will scale down the images to a size compatible with the constrained memory of devices. On macOS, this does nothing.
-     * This flag take no effect if `SDWebImageAvoidDecodeImage` is set. And it will be ignored if `SDWebImageProgressiveLoad` is set.
+     * To control the limit bytes, check `SDImageCoderHelper.defaultScaleDownLimitBytes` (Defaults to 60MB)
+     * This will actually translate to use context option `.imageThumbnailPixelSize` from v5.5.0 (Defaults to (3966, 3966)). Previously does not.
+     * This flags effect the progressive and animated images as well from v5.5.0. Previously does not.
+     * @note If you need detail controls, it's better to use context option `imageThumbnailPixelSize` and `imagePreserveAspectRatio` instead.
      */
     SDWebImageScaleDownLargeImages = 1 << 11,