Update the correct byte alignment and check with 8 * 4 bytes

The sd_isDecoded default value only check once

SDWebImage/Core/SDImageCoderHelper.h

@@ -79,6 +79,13 @@ static inline size_t SDByteAlign(size_t size, size_t alignment) {
  */
 + (CGBitmapInfo)preferredBitmapInfo:(BOOL)containsAlpha;
 
+/**
+ Check whether CGImage is hardware supported to rendering on screen, without the trigger of `CA::Render::copy_image`
+ You can debug the copied image by using Xcode's `Color Copied Image`, the copied image will turn Cyan and occupy double RAM for bitmap buffer.
+ Typically, when the CGImage's using the method above (`colorspace` / `byteAlignment` / `bitmapInfo`) can render withtout the copy.
+ */
++ (BOOL)CGImageIsHardwareSupported:(_Nonnull CGImageRef)cgImage;
+
 /**
  Check whether CGImage contains alpha channel.
  

SDWebImage/Core/SDImageCoderHelper.m

@@ -17,8 +17,11 @@
 #import "SDInternalMacros.h"
 #import "SDGraphicsImageRenderer.h"
 #import "SDInternalMacros.h"
+#import "SDDeviceHelper.h"
 #import <Accelerate/Accelerate.h>
 
+#define kCGColorSpaceDeviceRGB @"kCGColorSpaceDeviceRGB"
+
 #if SD_UIKIT
 static inline UIImage *SDImageDecodeUIKit(UIImage *image) {
     // See: https://developer.apple.com/documentation/uikit/uiimage/3750834-imagebypreparingfordisplay
@@ -296,13 +299,10 @@ static const CGFloat kDestSeemOverlap = 2.0f;   // the numbers of pixels to over
 }
 
 + (size_t)preferredByteAlignment {
-    // Actually the page size of system
-    static int __pageSize = 0;
-    static dispatch_once_t onceToken;
-    dispatch_once(&onceToken, ^{
-        __pageSize = getpagesize();
-    });
-    return __pageSize;
+    // https://github.com/path/FastImageCache#byte-alignment
+    // A properly aligned bytes-per-row value must be a multiple of 8 pixels × bytes per pixel.
+    // return [SDDeviceHelper cacheLineSize]; // Seems not the CPU cache line size
+    return 32;
 }
 
 + (CGBitmapInfo)preferredBitmapInfo:(BOOL)containsAlpha {
@@ -315,6 +315,36 @@ static const CGFloat kDestSeemOverlap = 2.0f;   // the numbers of pixels to over
     return CGImageGetBitmapInfo(cgImage);
 }
 
++ (BOOL)CGImageIsHardwareSupported:(CGImageRef)cgImage {
+    BOOL supported = YES;
+    // 1. Check byte alignment
+    size_t bytesPerRow = CGImageGetBytesPerRow(cgImage);
+    if (SDByteAlign(bytesPerRow, [SDImageCoderHelper preferredByteAlignment]) == bytesPerRow) {
+        // byte aligned, OK
+        supported &= YES;
+    } else {
+        // not aligned
+        supported &= NO;
+    }
+    if (!supported) return supported;
+    
+    // 2. Check color space
+    if (@available(iOS 10.0, tvOS 10.0, macOS 10.6, watchOS 3.0, *)) {
+        CGColorSpaceRef colorspace = CGImageGetColorSpace(cgImage);
+        NSString *colorspaceName = (__bridge_transfer NSString *)CGColorSpaceCopyName(colorspace);
+        // Seems sRGB/deviceRGB always supported, P3 not always
+        if ([colorspaceName isEqualToString:(__bridge NSString *)kCGColorSpaceSRGB] || [colorspaceName isEqualToString:kCGColorSpaceDeviceRGB]) {
+            supported &= YES;
+        } else {
+            supported &= NO;
+        }
+        return supported;
+    } else {
+        // Fallback on earlier versions
+        return supported;
+    }
+}
+
 + (BOOL)CGImageContainsAlpha:(CGImageRef)cgImage {
     if (!cgImage) {
         return NO;

SDWebImage/Core/UIImage+ForceDecode.m

@@ -20,25 +20,22 @@
     } else {
         // Assume only CGImage based can use lazy decoding
         CGImageRef cgImage = self.CGImage;
-        if (!cgImage) {
-            // Assume others as non-decoded
-            return NO;
-        }
-        CFStringRef uttype = CGImageGetUTType(self.CGImage);
-        if (uttype) {
-            // 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;
+        BOOL isDecoded;
+        if (cgImage) {
+            CFStringRef uttype = CGImageGetUTType(self.CGImage);
+            if (uttype) {
+                // Only ImageIO can set `com.apple.ImageIO.imageSourceTypeIdentifier`
+                isDecoded = NO;
             } else {
-                // not aligned, still need force-decode
-                return NO;
+                // Now, let's check if the CGImage is hardware supported (not byte-aligned will cause extra copy)
+                isDecoded = [SDImageCoderHelper CGImageIsHardwareSupported:cgImage];
             }
+        } else {
+            // Assume others as non-decoded
+            isDecoded = NO;
         }
+        objc_setAssociatedObject(self, @selector(sd_isDecoded), @(isDecoded), OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+        return isDecoded;
     }
 }
 

SDWebImage/Private/SDDeviceHelper.h

@@ -14,5 +14,6 @@
 
 + (NSUInteger)totalMemory;
 + (NSUInteger)freeMemory;
++ (size_t)cacheLineSize;
 
 @end

SDWebImage/Private/SDDeviceHelper.m

@@ -8,6 +8,7 @@
 
 #import "SDDeviceHelper.h"
 #import <mach/mach.h>
+#import <sys/sysctl.h>
 
 @implementation SDDeviceHelper
 
@@ -29,4 +30,18 @@
     return vm_stat.free_count * page_size;
 }
 
++ (size_t)cacheLineSize {
+    size_t size;
+    sysctlbyname("hw.cachelinesize", NULL, &size, NULL, 0);
+    char *info = malloc(size);
+    sysctlbyname("hw.cachelinesize", info, &size, NULL, 0);
+    if (strlen(info)) {
+        // hardcode
+        return 64;
+    }
+    char *end;
+    long result = strtol(info, &end, 10);
+    return result;
+}
+
 @end