iOS MethodChannel code

ios/Classes/FlutterNeatPdfViewer.h

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+#import <Flutter/Flutter.h>
+
+@interface FlutterNeatPdfViewer : NSObject<FlutterPlugin>
+@end

ios/Classes/FlutterNeatPdfViewer.m

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+#import "FlutterNeatPdfViewer.h"
+
+static NSString* const kDirectory = @"FlutterPluginPdfViewer";
+static NSString* const kFilePath = @"file:///";
+static NSString* kFileName = @"";
+
+@implementation FlutterNeatPdfViewer
++ (void)registerWithRegistrar:(NSObject<FlutterPluginRegistrar>*)registrar {
+  FlutterMethodChannel* channel = [FlutterMethodChannel
+      methodChannelWithName:@"flutter_plugin_pdf_viewer"
+            binaryMessenger:[registrar messenger]];
+  FlutterNeatPdfViewer* instance = [[FlutterNeatPdfViewer alloc] init];
+  [registrar addMethodCallDelegate:instance channel:channel];
+}
+
+- (void)handleMethodCall:(FlutterMethodCall*)call result:(FlutterResult)result {
+  dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
+          if ([@"getPage" isEqualToString:call.method]) {
+              size_t pageNumber = (size_t)[call.arguments[@"pageNumber"] intValue];
+              NSString * filePath = call.arguments[@"filePath"];
+              result([self getPage:filePath ofPage:pageNumber]);
+          } else if ([@"getNumberOfPages" isEqualToString:call.method]) {
+              NSString * filePath = call.arguments[@"filePath"];
+              result([self getNumberOfPages:filePath]);
+          }
+          else {
+              result(FlutterMethodNotImplemented);
+          }
+      });
+}
+
+-(NSString *)getNumberOfPages:(NSString *)url
+{
+    NSURL * sourcePDFUrl;
+    if([url containsString:kFilePath]){
+        sourcePDFUrl = [NSURL URLWithString:url];
+    }else{
+        sourcePDFUrl = [NSURL URLWithString:[kFilePath stringByAppendingString:url]];
+    }
+    CGPDFDocumentRef SourcePDFDocument = CGPDFDocumentCreateWithURL((__bridge CFURLRef)sourcePDFUrl);
+    size_t numberOfPages = CGPDFDocumentGetNumberOfPages(SourcePDFDocument);
+    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
+    NSString *temporaryDirectory = [paths objectAtIndex:0];
+    NSString *filePathAndDirectory = [temporaryDirectory stringByAppendingPathComponent:kDirectory];
+    NSError *error;
+
+    // Clear cache folder
+    if ([[NSFileManager defaultManager] fileExistsAtPath:filePathAndDirectory]) {
+        NSLog(@"[FlutterPluginPDFViewer] Removing old documents cache");
+        [[NSFileManager defaultManager] removeItemAtPath:filePathAndDirectory error:&error];
+    }
+
+    if (![[NSFileManager defaultManager] createDirectoryAtPath:filePathAndDirectory
+                                   withIntermediateDirectories:YES
+                                                    attributes:nil
+                                                         error:&error])
+    {
+        NSLog(@"Create directory error: %@", error);
+        return nil;
+    }
+    // Generate random file size for this document
+
+    kFileName = [[NSUUID UUID] UUIDString];
+    NSLog(@"[FlutterPluginPdfViewer] File has %zd pages", numberOfPages);
+    NSLog(@"[FlutterPluginPdfViewer] File will be saved in cache as %@", kFileName);
+    return [NSString stringWithFormat:@"%zd", numberOfPages];
+}
+
+-(NSString*)getPage:(NSString *)url ofPage:(size_t)pageNumber
+{
+    NSURL * sourcePDFUrl;
+    if([url containsString:kFilePath]){
+        sourcePDFUrl = [NSURL URLWithString:url];
+    }else{
+        sourcePDFUrl = [NSURL URLWithString:[kFilePath stringByAppendingString:url]];
+    }
+    CGPDFDocumentRef SourcePDFDocument = CGPDFDocumentCreateWithURL((__bridge CFURLRef)sourcePDFUrl);
+    size_t numberOfPages = CGPDFDocumentGetNumberOfPages(SourcePDFDocument);
+    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
+    NSString *temporaryDirectory = [paths objectAtIndex:0];
+    NSString *filePathAndDirectory = [temporaryDirectory stringByAppendingPathComponent:kDirectory];
+    NSError *error;
+
+    if (pageNumber > numberOfPages) {
+        pageNumber = numberOfPages;
+    }
+
+    if (![[NSFileManager defaultManager] createDirectoryAtPath:filePathAndDirectory
+                                   withIntermediateDirectories:YES
+                                                    attributes:nil
+                                                         error:&error])
+    {
+        NSLog(@"Create directory error: %@", error);
+        return nil;
+    }
+    CGPDFPageRef SourcePDFPage = CGPDFDocumentGetPage(SourcePDFDocument, pageNumber);
+    CGPDFPageRetain(SourcePDFPage);
+    NSString *relativeOutputFilePath = [NSString stringWithFormat:@"%@/%@-%d.png", kDirectory, kFileName, (int)pageNumber];
+    NSString *imageFilePath = [temporaryDirectory stringByAppendingPathComponent:relativeOutputFilePath];
+    CGRect sourceRect = CGPDFPageGetBoxRect(SourcePDFPage, kCGPDFMediaBox);
+    UIGraphicsBeginPDFContextToFile(imageFilePath, sourceRect, nil);
+    // Calculate resolution
+    // Set DPI to 300
+    CGFloat dpi = 300.0 / 72.0;
+    CGFloat width = sourceRect.size.width * dpi;
+    CGFloat height = sourceRect.size.height * dpi;
+    UIGraphicsBeginImageContext(CGSizeMake(width, height));
+    // Fill Background
+    CGContextRef currentContext = UIGraphicsGetCurrentContext();
+    // Change interpolation settings
+    CGContextSetInterpolationQuality(currentContext, kCGInterpolationHigh);
+    // Fill background with white color
+    CGContextSetRGBFillColor(currentContext, 1.0f, 1.0f, 1.0f, 1.0f);
+    CGContextFillRect(currentContext, CGContextGetClipBoundingBox(currentContext));
+    CGContextTranslateCTM(currentContext, 0.0, height);
+    CGContextScaleCTM(currentContext, dpi, -dpi);
+    CGContextSaveGState(currentContext);
+    CGContextDrawPDFPage (currentContext, SourcePDFPage);
+    CGContextRestoreGState(currentContext);
+    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
+    UIGraphicsEndImageContext();
+    [UIImagePNGRepresentation(image) writeToFile: imageFilePath atomically:YES];
+    return imageFilePath;
+}
+
+@end

ios/flutter_neat_pdf_viewer.podspec

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+#
+# To learn more about a Podspec see http://guides.cocoapods.org/syntax/podspec.html
+#
+Pod::Spec.new do |s|
+  s.name             = 'flutter_neat_pdf_viewer'
+  s.version          = '0.0.1'
+  s.summary          = 'Allows you to generate PNG's of specified pages from a provided PDF file source.'
+  s.description      = <<-DESC
+Allows you to generate PNG&#x27;s of specified pages from a provided PDF file source.
+                       DESC
+  s.homepage         = 'http://example.com'
+  s.license          = { :file => '../LICENSE' }
+  s.author           = { 'Your Company' => 'email@example.com' }
+  s.source           = { :path => '.' }
+  s.source_files = 'Classes/**/*'
+  s.public_header_files = 'Classes/**/*.h'
+  s.dependency 'Flutter'
+
+  s.ios.deployment_target = '11.0'
+end
+