Add a option to allow advanced user to prefer bitmap version, instead of vector image format for PDF. Do refactory for implementation

dreampiggy · dreampiggy · commit 36eb9b06045c · 2018-10-31T17:48:22.000+08:00
diff --git a/SDWebImagePDFCoder/Classes/SDImagePDFCoder.m b/SDWebImagePDFCoder/Classes/SDImagePDFCoder.m
@@ -7,6 +7,7 @@
 
 #import "SDImagePDFCoder.h"
 #import "SDWebImagePDFCoderDefine.h"
+#import "objc/runtime.h"
 
 #define SD_FOUR_CC(c1,c2,c3,c4) ((uint32_t)(((c4) << 24) | ((c3) << 16) | ((c2) << 8) | (c1)))
 
@@ -22,6 +23,92 @@ + (instancetype)_imageWithCGPDFPage:(CGPDFPageRef)page scale:(double)scale orien
 @end
 #endif
 
+#if SD_MAC
+static void *kNSGraphicsContextScaleFactorKey;
+
+static CGContextRef SDCGContextCreateBitmapContext(CGSize size, BOOL opaque, CGFloat scale) {
+    if (scale == 0) {
+        // Match `UIGraphicsBeginImageContextWithOptions`, reset to the scale factor of the device’s main screen if scale is 0.
+        scale = [NSScreen mainScreen].backingScaleFactor;
+    }
+    size_t width = ceil(size.width * scale);
+    size_t height = ceil(size.height * scale);
+    if (width < 1 || height < 1) return NULL;
+    
+    //pre-multiplied BGRA for non-opaque, BGRX for opaque, 8-bits per component, as Apple's doc
+    CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
+    CGImageAlphaInfo alphaInfo = kCGBitmapByteOrder32Host | (opaque ? kCGImageAlphaNoneSkipFirst : kCGImageAlphaPremultipliedFirst);
+    CGContextRef context = CGBitmapContextCreate(NULL, width, height, 8, 0, space, kCGBitmapByteOrderDefault | alphaInfo);
+    CGColorSpaceRelease(space);
+    if (!context) {
+        return NULL;
+    }
+    CGContextScaleCTM(context, scale, scale);
+    
+    return context;
+}
+#endif
+
+static void SDGraphicsBeginImageContextWithOptions(CGSize size, BOOL opaque, CGFloat scale) {
+#if SD_UIKIT || SD_WATCH
+    UIGraphicsBeginImageContextWithOptions(size, opaque, scale);
+#else
+    CGContextRef context = SDCGContextCreateBitmapContext(size, opaque, scale);
+    if (!context) {
+        return;
+    }
+    NSGraphicsContext *graphicsContext = [NSGraphicsContext graphicsContextWithCGContext:context flipped:NO];
+    objc_setAssociatedObject(graphicsContext, &kNSGraphicsContextScaleFactorKey, @(scale), OBJC_ASSOCIATION_RETAIN);
+    CGContextRelease(context);
+    [NSGraphicsContext saveGraphicsState];
+    NSGraphicsContext.currentContext = graphicsContext;
+#endif
+}
+
+static CGContextRef SDGraphicsGetCurrentContext(void) {
+#if SD_UIKIT || SD_WATCH
+    return UIGraphicsGetCurrentContext();
+#else
+    return NSGraphicsContext.currentContext.CGContext;
+#endif
+}
+
+static void SDGraphicsEndImageContext(void) {
+#if SD_UIKIT || SD_WATCH
+    UIGraphicsEndImageContext();
+#else
+    [NSGraphicsContext restoreGraphicsState];
+#endif
+}
+
+static UIImage * SDGraphicsGetImageFromCurrentImageContext(void) {
+#if SD_UIKIT || SD_WATCH
+    return UIGraphicsGetImageFromCurrentImageContext();
+#else
+    NSGraphicsContext *context = NSGraphicsContext.currentContext;
+    CGContextRef contextRef = context.CGContext;
+    if (!contextRef) {
+        return nil;
+    }
+    CGImageRef imageRef = CGBitmapContextCreateImage(contextRef);
+    if (!imageRef) {
+        return nil;
+    }
+    CGFloat scale = 0;
+    NSNumber *scaleFactor = objc_getAssociatedObject(context, &kNSGraphicsContextScaleFactorKey);
+    if ([scaleFactor isKindOfClass:[NSNumber class]]) {
+        scale = scaleFactor.doubleValue;
+    }
+    if (!scale) {
+        // reset to the scale factor of the device’s main screen if scale is 0.
+        scale = [NSScreen mainScreen].backingScaleFactor;
+    }
+    NSImage *image = [[NSImage alloc] initWithCGImage:imageRef scale:scale orientation:kCGImagePropertyOrientationUp];
+    CGImageRelease(imageRef);
+    return image;
+#endif
+}
+
 @implementation SDImagePDFCoder
 
 + (SDImagePDFCoder *)sharedCoder {
@@ -43,13 +130,17 @@ - (UIImage *)decodedImageWithData:(NSData *)data options:(SDImageCoderOptions *)
     }
     
     NSUInteger pageNumber = 0;
+    BOOL preferredBitmap = NO;
     CGSize imageSize = CGSizeZero;
     BOOL preserveAspectRatio = YES;
     // Parse args
     SDWebImageContext *context = options[SDImageCoderWebImageContext];
     if (context[SDWebImageContextPDFPageNumber]) {
         pageNumber = [context[SDWebImageContextPDFPageNumber] unsignedIntegerValue];
     }
+    if (context[SDWebImageContextPDFPerferredBitmap]) {
+        preferredBitmap = [context[SDWebImageContextPDFPerferredBitmap] boolValue];
+    }
     if (context[SDWebImageContextPDFImageSize]) {
         NSValue *sizeValue = context[SDWebImageContextPDFImageSize];
 #if SD_UIKIT
@@ -62,7 +153,14 @@ - (UIImage *)decodedImageWithData:(NSData *)data options:(SDImageCoderOptions *)
         preserveAspectRatio = [context[SDWebImageContextPDFImagePreserveAspectRatio] boolValue];
     }
     
-    UIImage *image = [self sd_createPDFImageWithData:data pageNumber:pageNumber targetSize:imageSize preserveAspectRatio:preserveAspectRatio];
+    UIImage *image;
+    if (!preferredBitmap && [self.class supportsVectorPDFImage]) {
+        image = [self createVectorPDFWithData:data pageNumber:pageNumber];
+    } else {
+        image = [self createBitmapPDFWithData:data pageNumber:pageNumber targetSize:imageSize preserveAspectRatio:preserveAspectRatio];
+    }
+    
+    image.sd_imageFormat = SDImageFormatPDF;
     
     return image;
 }
@@ -76,8 +174,8 @@ - (NSData *)encodedDataWithImage:(UIImage *)image format:(SDImageFormat)format o
     return nil;
 }
 
-// Using Core Graphics to draw PDF but not PDFKit(iOS 11+/macOS 10.4+) to keep old firmware compatible
-- (UIImage *)sd_createPDFImageWithData:(nonnull NSData *)data pageNumber:(NSUInteger)pageNumber targetSize:(CGSize)targetSize preserveAspectRatio:(BOOL)preserveAspectRatio {
+#pragma mark - Vector PDF representation
+- (UIImage *)createVectorPDFWithData:(nonnull NSData *)data pageNumber:(NSUInteger)pageNumber {
     NSParameterAssert(data);
     UIImage *image;
     
@@ -87,12 +185,10 @@ - (UIImage *)sd_createPDFImageWithData:(nonnull NSData *)data pageNumber:(NSUInt
     if (!imageRep) {
         return nil;
     }
-    imageRep.currentPage = pageNumber
+    imageRep.currentPage = pageNumber;
     image = [[NSImage alloc] initWithSize:imageRep.size];
     [image addRepresentation:imageRep];
-    
 #else
-    
     CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
     if (!provider) {
         return nil;
@@ -110,11 +206,33 @@ - (UIImage *)sd_createPDFImageWithData:(nonnull NSData *)data pageNumber:(NSUInt
         return nil;
     }
     
-    // Check if we can use built-in PDF image support, instead of draw bitmap
-    if ([[self class] supportsBuiltInPDFImage]) {
-        UIImage *image = [UIImage _imageWithCGPDFPage:page];
+    image = [UIImage _imageWithCGPDFPage:page];
+    CGPDFDocumentRelease(document);
+#endif
+    
+    return image;
+}
+
+#pragma mark - Bitmap PDF representation
+- (UIImage *)createBitmapPDFWithData:(nonnull NSData *)data pageNumber:(NSUInteger)pageNumber targetSize:(CGSize)targetSize preserveAspectRatio:(BOOL)preserveAspectRatio {
+    NSParameterAssert(data);
+    UIImage *image;
+    
+    CGDataProviderRef provider = CGDataProviderCreateWithCFData((__bridge CFDataRef)data);
+    if (!provider) {
+        return nil;
+    }
+    CGPDFDocumentRef document = CGPDFDocumentCreateWithProvider(provider);
+    CGDataProviderRelease(provider);
+    if (!document) {
+        return nil;
+    }
+    
+    // `CGPDFDocumentGetPage` page number is 1-indexed.
+    CGPDFPageRef page = CGPDFDocumentGetPage(document, pageNumber + 1);
+    if (!page) {
         CGPDFDocumentRelease(document);
-        return image;
+        return nil;
     }
     
     CGPDFBox box = kCGPDFCropBox;
@@ -134,31 +252,33 @@ - (UIImage *)sd_createPDFImageWithData:(nonnull NSData *)data pageNumber:(NSUInt
     CGAffineTransform scaleTransform = CGAffineTransformMakeScale(xScale, yScale);
     CGAffineTransform transform = CGPDFPageGetDrawingTransform(page, box, drawRect, 0, preserveAspectRatio);
     
-    UIGraphicsBeginImageContextWithOptions(targetRect.size, NO, 0);
-    CGContextRef context = UIGraphicsGetCurrentContext();
+    SDGraphicsBeginImageContextWithOptions(targetRect.size, NO, 0);
+    CGContextRef context = SDGraphicsGetCurrentContext();
     
-    // Core Graphics coordinate system use the bottom-left, iOS use the flipped one
+#if SD_UIKIT
+    // Core Graphics coordinate system use the bottom-left, UIkit use the flipped one
     CGContextTranslateCTM(context, 0, targetRect.size.height);
     CGContextScaleCTM(context, 1, -1);
+#endif
     
     CGContextConcatCTM(context, scaleTransform);
     CGContextConcatCTM(context, transform);
     
     CGContextDrawPDFPage(context, page);
     
-    image = UIGraphicsGetImageFromCurrentImageContext();
-    UIGraphicsEndImageContext();
+    image = SDGraphicsGetImageFromCurrentImageContext();
+    SDGraphicsEndImageContext();
     
     CGPDFDocumentRelease(document);
-#endif
-    
-    image.sd_imageFormat = SDImageFormatPDF;
     
     return image;
 }
 
-#if SD_UIKIT
-+ (BOOL)supportsBuiltInPDFImage {
++ (BOOL)supportsVectorPDFImage {
+#if SD_MAC
+    // macOS's `NSImage` supports PDF built-in rendering
+    return YES;
+#else
     static dispatch_once_t onceToken;
     static BOOL supports;
     dispatch_once(&onceToken, ^{
@@ -170,8 +290,8 @@ + (BOOL)supportsBuiltInPDFImage {
         }
     });
     return supports;
-}
 #endif
+}
 
 + (BOOL)isPDFFormatForData:(NSData *)data {
     if (!data) {
diff --git a/SDWebImagePDFCoder/Classes/SDWebImagePDFCoderDefine.h b/SDWebImagePDFCoder/Classes/SDWebImagePDFCoderDefine.h
@@ -15,6 +15,13 @@ NS_ASSUME_NONNULL_BEGIN
  */
 FOUNDATION_EXPORT SDWebImageContextOption _Nonnull const SDWebImageContextPDFPageNumber;
 
+/**
+ A BOOL value which specify whether we prefer the actual bitmap representation instead of vector representation for PDF image. This is because the UIImage on iOS 11+ (NSImgae on macOS) can use the vector image format, which support dynamic scale without losing any detail. However, for some image processing logic, user may need the actual bitmap representation to manage pixels. Also, for lower firmware on iOS, the `UIImage` does not support vector rendering, user may want to handle them using the same code. (NSNumber)
+ If you don't provide this value, use NO for default value and prefer the vector format when possible.
+ */
+FOUNDATION_EXPORT SDWebImageContextOption _Nonnull const SDWebImageContextPDFPerferredBitmap;
+
+#pragma mark - Bitmap Representation Options
 /**
  A CGSize raw value which specify the desired PDF image size during image loading. Because vector image like PDF format, may not contains a fixed size, or you want to get a larger size bitmap representation UIImage. (NSValue)
  If you don't provide this value, use the PDF cropBox size instead.
diff --git a/SDWebImagePDFCoder/Classes/SDWebImagePDFCoderDefine.m b/SDWebImagePDFCoder/Classes/SDWebImagePDFCoderDefine.m
@@ -8,5 +8,6 @@
 #import "SDWebImagePDFCoderDefine.h"
 
 SDWebImageContextOption _Nonnull const SDWebImageContextPDFPageNumber = @"pdfPageNumber";
+SDWebImageContextOption _Nonnull const SDWebImageContextPDFPerferredBitmap = @"pdfPerferredBitmap";
 SDWebImageContextOption _Nonnull const SDWebImageContextPDFImageSize = @"pdfImageSize";
 SDWebImageContextOption _Nonnull const SDWebImageContextPDFImagePreserveAspectRatio = @"pdfImagePreserveAspectRatio";
