Add support to easy export("encoding") the SVG data of SVGKImage representation

Author: dreampiggy

Example/Podfile

@@ -3,6 +3,7 @@ use_frameworks!
 target 'SDWebImageSVGCoder_Example' do
   platform :ios, '9.3'
   pod 'SDWebImageSVGCoder', :path => '../'
+  pod 'SVGKit', :git => 'https://github.com/SVGKit/SVGKit.git', :branch => '3.x'
 
   target 'SDWebImageSVGCoder_Tests' do
     inherit! :search_paths

Example/Podfile.lock

@@ -1,33 +1,41 @@
 PODS:
-  - CocoaLumberjack (3.5.2):
-    - CocoaLumberjack/Core (= 3.5.2)
-  - CocoaLumberjack/Core (3.5.2)
-  - SDWebImage/Core (5.0.0)
-  - SDWebImageSVGCoder (0.1.1):
+  - CocoaLumberjack (3.5.3):
+    - CocoaLumberjack/Core (= 3.5.3)
+  - CocoaLumberjack/Core (3.5.3)
+  - SDWebImage/Core (5.0.2)
+  - SDWebImageSVGCoder (0.2.0):
     - SDWebImage/Core (~> 5.0)
     - SVGKit (>= 2.1)
   - SVGKit (2.1.0):
     - CocoaLumberjack (~> 3.0)
 
 DEPENDENCIES:
   - SDWebImageSVGCoder (from `../`)
+  - SVGKit (from `https://github.com/SVGKit/SVGKit.git`, branch `3.x`)
 
 SPEC REPOS:
   https://github.com/cocoapods/specs.git:
     - CocoaLumberjack
     - SDWebImage
-    - SVGKit
 
 EXTERNAL SOURCES:
   SDWebImageSVGCoder:
     :path: "../"
+  SVGKit:
+    :branch: 3.x
+    :git: https://github.com/SVGKit/SVGKit.git
+
+CHECKOUT OPTIONS:
+  SVGKit:
+    :commit: cf32da55633e370e66a7ba6e003224bd67296c16
+    :git: https://github.com/SVGKit/SVGKit.git
 
 SPEC CHECKSUMS:
-  CocoaLumberjack: 118bf4a820efc641f79fa487b75ed928dccfae23
-  SDWebImage: 5de80a0302de9e377e62f47d2fa1304efff0e55f
-  SDWebImageSVGCoder: 6a369e2a2cacb24de6db073346d5076834471a55
+  CocoaLumberjack: 2f44e60eb91c176d471fdba43b9e3eae6a721947
+  SDWebImage: 6764b5fa0f73c203728052955dbefa2bf1f33282
+  SDWebImageSVGCoder: 61f60a3064db079de646a34a5f5aa8d3ac258345
   SVGKit: 8a2fc74258bdb2abb54d3b65f3dd68b0277a9c4d
 
-PODFILE CHECKSUM: 5438d217c00bb7b2da72c6e8ce8ec9db055a4cc6
+PODFILE CHECKSUM: 8107c7193dd0c4844a782937610f415caa6ef482
 
 COCOAPODS: 1.6.1

Example/SDWebImageSVGCoder-Example-macOS/ViewController.m

@@ -35,6 +35,8 @@ - (void)viewDidLoad {
     [imageView1 sd_setImageWithURL:SVGURL placeholderImage:nil options:SDWebImageRetryFailed completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
         if (image) {
             NSLog(@"SVG load success");
+            NSData *svgData = [image sd_imageDataAsFormat:SDImageFormatSVG];
+            NSAssert(svgData.length > 0, @"SVG Data should exist");
         }
     }];
     [imageView2 sd_setImageWithURL:SVGURL2 placeholderImage:nil options:SDWebImageRetryFailed context:@{SDWebImageContextSVGImageSize : @(imageView2.bounds.size)} progress:nil completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {

Example/SDWebImageSVGCoder/SDViewController.m

@@ -51,6 +51,8 @@ - (void)viewDidLoad
     [imageView1 sd_setImageWithURL:svgURL placeholderImage:nil options:SDWebImageRetryFailed completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {
         if (image) {
             NSLog(@"SVGKLayeredImageView SVG load success");
+            NSData *svgData = [image sd_imageDataAsFormat:SDImageFormatSVG];
+            NSAssert(svgData.length > 0, @"SVG Data should exist");
         }
     }];
     [imageView2 sd_setImageWithURL:svgURL2 placeholderImage:nil options:SDWebImageRetryFailed completed:^(UIImage * _Nullable image, NSError * _Nullable error, SDImageCacheType cacheType, NSURL * _Nullable imageURL) {

SDWebImageSVGCoder/Classes/SDImageSVGCoder.m

@@ -6,6 +6,7 @@
 //
 
 #import "SDImageSVGCoder.h"
+#import "SDSVGImage.h"
 #import "SDWebImageSVGCoderDefine.h"
 #import <SVGKit/SVGKit.h>
 
@@ -76,11 +77,24 @@ - (UIImage *)decodedImageWithData:(NSData *)data options:(SDImageCoderOptions *)
 #pragma mark - Encode
 
 - (BOOL)canEncodeToFormat:(SDImageFormat)format {
-    return NO;
+    return format == SDImageFormatSVG;
 }
 
 - (NSData *)encodedDataWithImage:(UIImage *)image format:(SDImageFormat)format options:(SDImageCoderOptions *)options {
-    return nil;
+    // Only support SVGKImage wrapper
+    if (![image isKindOfClass:SDSVGImage.class]) {
+        return nil;
+    }
+    SVGKImage *svgImage = ((SDSVGImage *)image).SVGImage;
+    if (!svgImage) {
+        return nil;
+    }
+    SVGKSource *source = svgImage.source;
+    // Should be NSData type source
+    if (![source isKindOfClass:SVGKSourceNSData.class]) {
+        return nil;
+    }
+    return ((SVGKSourceNSData *)source).rawData;
 }
 
 #pragma mark - Helper