Update the Example and Readme about the new context option

Author: dreampiggy

Example/SDWebImageSVGCoder/SDViewController.m

@@ -65,7 +65,7 @@ - (void)viewDidLoad
             }];
         }
     }];
-    [imageView3 sd_setImageWithURL:svgURL3 placeholderImage:nil options:SDWebImageRetryFailed context:@{SDWebImageContextSVGPrefersBitmap: @(YES), SDWebImageContextSVGImageSize: @(CGSizeMake(100, 100))} progress:nil completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
+    [imageView3 sd_setImageWithURL:svgURL3 placeholderImage:nil options:SDWebImageRetryFailed context:@{SDWebImageContextImageThumbnailPixelSize: @(CGSizeMake(100, 100))} progress:nil completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
         if (image) {
             NSLog(@"SVG bitmap load success.");
             NSData *svgData = [image sd_imageDataAsFormat:SDImageFormatSVG];

README.md

@@ -59,7 +59,7 @@ SDWebImageSVGCoder is available through [Swift Package Manager](https://swift.or
 ```swift
 let package = Package(
     dependencies: [
-        .package(url: "https://github.com/SDWebImage/SDWebImageSVGCoder.git", from: "1.0")
+        .package(url: "https://github.com/SDWebImage/SDWebImageSVGCoder.git", from: "1.4")
     ]
 )
 ```
@@ -108,24 +108,26 @@ Note since UIImageView/NSImageView support this vector rendering, it means this
 
 ### Render SVG as bitmap image
 
-In most cases, vector SVG is preferred. But however, sometimes you may want the bitmap form of SVG, used for image processing. You can use `.svgPrefersBitmap` to provide the bitmap format as well.
+In most cases, vector SVG is preferred. But however, sometimes you may want the bitmap form of SVG, used for image processing.
 
-By default it use the SVG canvas size. You can also specify a desired size during image loading using `.svgImageSize` context option. And you can specify whether or not to keep aspect ratio during scale using `.svgImagePreserveAspectRatio` context option.
+By default it use the SVG viewBox size. You can also specify a desired size during image loading using `.imageThumbnailPixelSize` context option. And you can specify whether or not to keep aspect ratio during scale using `.imagePreserveAspectRatio` context option.
+
+Note: Once you pass the pixel size, we will always generate the bitmap representation even on iOS/tvOS 11+. If you want the vector format, do not pass them, let `UIImageView` to dynamically stretch the SVG.
 
 + Objective-C
 
 ```objectivec
 UIImageView *imageView;
-CGSize SVGImageSize = CGSizeMake(500, 500);
-[imageView sd_setImageWithURL:url placeholderImage:nil options:0 context:@{SDWebImageContextSVGPrefersBitmap: @YES, SDWebImageContextSVGImageSize: @(SVGImageSize)];
+CGSize bitmapSize = CGSizeMake(500, 500);
+[imageView sd_setImageWithURL:url placeholderImage:nil options:0 context:@{SDWebImageContextThumbnailPixelSize: @(bitmapSize)];
 ```
 
 + Swift
 
 ```swift
 let imageView: UIImageView
-let SVGImageSize = CGSize(width: 500, height: 500)
-imageView.sd_setImage(with: url, placeholderImage: nil, options: [], context: [.svgPrefersBitmap : true, .svgImageSize : SVGImageSize])
+let bitmapSize = CGSize(width: 500, height: 500)
+imageView.sd_setImage(with: url, placeholderImage: nil, options: [], context: [.imageThumbnailPixelSize : bitmapSize])
 ```
 
 ## Export SVG data
@@ -137,15 +139,19 @@ Note: The bitmap form of SVG does not support SVG data export.
 + Objective-C
 
 ```objectivec
-UIImage *image = imageView.image; // Image generated by this coder plugin
-NSData *imageData = [image sd_imageDataAsFormat:SDImageFormatSVG];
+UIImage *svgImage; // UIImage with vector image, or NSImage contains `NSSVGImageRep`
+if (svgImage.sd_isVector) { // This API available in SDWebImage 5.6.0
+    NSData *svgData = [svgImage sd_imageDataAsFormat:SDImageFormatSVG];
+}
 ```
 
 + Swift
 
 ```swift
-let image = imageView.image // Image generated by this coder plugin 
-let imageData = image.sd_imageData(as: .SVG)
+let svgImage: UIImage // UIImage with vector image, or NSImage contains `NSSVGImageRep`
+if svgImage.sd_isVector { // This API available in SDWebImage 5.6.0
+    let svgData = svgImage.sd_imageData(as: .SVG)
+}
 ```
 
 ## Backward Deployment