React Native iOS Watermark

CreateImage.h

//
//  CreateImage.h
//  Created by Mohammad Julfikar on 28/06/2019.
//  Copyright © 2019 Facebook. All rights reserved.
//

#import "RCTBridgeModule.h"
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface CreateImage : NSObject<RCTBridgeModule>

@end

NS_ASSUME_NONNULL_END

CreateImage.m

//
//  CreateImage.m
//
//  Created by Mohammad Julfikar on 28/06/2019.
//  Copyright © 2019 Facebook. All rights reserved.
//

#import "CreateImage.h"


@implementation CreateImage

RCT_EXPORT_MODULE();
RCT_EXPORT_METHOD(imagePath:(NSString*)path watermark:(NSString*)watermark newPath:(RCTResponseSenderBlock)callback){
  
  NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *documentsDirectory = [paths objectAtIndex:0];
  NSString *tempImagePath = [documentsDirectory stringByAppendingPathComponent: [NSString stringWithFormat:@"%@", @"share.jpeg"]];
  
  NSError *error = nil;
  BOOL msg = [[NSFileManager defaultManager] removeItemAtPath:tempImagePath error:&error];
  
  if(!msg){
    NSLog(@"Temp watermark FAILED to delete... Path ->%@",tempImagePath);
  }
  NSString *tempWatermark = [NSString stringWithFormat:@"%@",watermark];
  UIImage *current =[UIImage imageWithContentsOfFile:path];
  
  int width = current.size.width;
  int height = current.size.height;
  
  if(width == 0){
      return;
  }
  
  int minimalRate = 2;
  int fontSize = 12;
  int reserved = 100;
  if(width / 1000 > 2){
      minimalRate = width / 1000;
      fontSize += minimalRate + 4;
  }
  
  int todoWidth = width / minimalRate;
  int todoHeight = height / minimalRate;

  if(height < 1000 || width < 1000){
      todoWidth = width;
      todoHeight = height;
  }
  
  int canvasHeight = todoHeight + reserved;
  
  UIGraphicsBeginImageContext(CGSizeMake(todoWidth, todoHeight));
  [current drawInRect:CGRectMake(0, 0, todoWidth, todoHeight)];
  UIImage *resizedImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  
  UIView *tcv = [[UIView alloc] initWithFrame:CGRectMake(0, 0, todoWidth, canvasHeight)];
  [tcv setBackgroundColor:[UIColor blackColor]];
  
  CGSize gcSize = tcv.frame.size;
  UIGraphicsBeginImageContext(gcSize);
  
  [tcv.layer renderInContext:UIGraphicsGetCurrentContext()];
  UIImage *blankImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  
  UIGraphicsBeginImageContextWithOptions(blankImage.size, FALSE, 0.0);
  [blankImage drawInRect:CGRectMake( 0, 0, todoWidth, canvasHeight)];
  [resizedImage drawInRect:CGRectMake( 0, 0, todoWidth, todoHeight)];
  UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  
  UIColor *fontColor = [UIColor whiteColor];
  
  UIGraphicsBeginImageContextWithOptions(newImage.size, YES, 0.0f);
  [newImage drawInRect:CGRectMake(0,0,newImage.size.width,newImage.size.height)];
  CGRect rect = CGRectMake(10, todoHeight+10, newImage.size.width, newImage.size.height);
  [[UIColor whiteColor] set];
  
  UIFont *font = [UIFont boldSystemFontOfSize:fontSize];
  
  if([watermark respondsToSelector:@selector(drawInRect:withAttributes:)])
  {
      NSDictionary *att = [NSDictionary dictionaryWithObjects:
                           @[font, fontColor]
                                                      forKeys:
                           @[NSFontAttributeName, NSForegroundColorAttributeName]];
      [watermark drawInRect:rect withAttributes:att];
  }
  else
  {
      [watermark drawInRect:CGRectIntegral(rect) withFont:font];
  }
  
  newImage = UIGraphicsGetImageFromCurrentImageContext();
  UIGraphicsEndImageContext();
  
  NSData *imageData = UIImageJPEGRepresentation(newImage, 0.85f);
  [imageData writeToFile:tempImagePath atomically:YES];
  
  callback(@[tempImagePath]);
  
}

@end