Post-processing of the Image Failed If This is a photo or a Large Image Scale It Down to 2500 Pixels
To avoid this type of error, you can modify your images before you upload them. It will help you uploading error free images. WordPress recently updated their requirements on media file uploading in server.
If you experienced the error message "Post-processing of the image failed. If this is a photo or a large image, please scale it down to 2500 pixels and upload it again", you should watch the video carefully.
There is no exact solution of this error, but we can try to solve the issue implementing some techniques. This will help you editing and updating the issues effectively. You will able to handle the error following some common tricks.
The problem happens for browser caching that you can easily fix clearing the browser cache files. You can also upload images from the Media Library option and the problem will be fixed. I experienced the same issue on my website after the WordPress Version update and did research on it.
Finally, I got a solution and I created the video to help more people who is experiencing the same issue on their website. I know how you feel when you can't upload images on your website and you don't get any solution.
How to Fix Post Processing Error in WordPress?
I had a quick fix on my website for this error. But most of the people are not getting the solution from the video. I did further research and list few more possible ways. Hope these methods will help you.
Method 1: Clear Browser Caching
Method 2: Upload Image Using Media Uploader
Method 3: Disable "BIG Image" Threshold
Method 4: Downgrade WordPress Version
Clear Browser Caching: This is one of the reason you experiencing the issue of uploading image. You should clear all the caching from the browser and check if the uploading process working or not. If you don't get the solution, you should try the 2nd method.
Upload Image from Media Library: You should visit Media > Add New option from your WordPress dashboard. Then upload an image using the upload option. This will remove the error and you can upload new images easily.
Disable "BIG Image" Threshold: This is a great plugin by Jonathan Desrosiers that helps you getting quick fix from the error. You can download "Disable "BIG Image" Threshold" plugins from WordPress Theme directory and use it to fix the problem.
Recent WordPress 5.3 update bring a limitation for the larger images more than 2500px. This plugins will help you to fix the error. However, few people blamed the plugin is not working for them. But I suggest you to try the plugin at least to check.
Downgrade the WordPress Version: Most of the people has the common blame that they are experiencing the issue after upgrading their WordPress version. If you also think the latest version is causing the problem, you can downgrade the WordPress version to check. WordPress will fix the error quick and you can than upgrade the version.
More Solutions from WordPress.org Forum:
How to Disable Post-processing Image Error WordPress?
Rather adding this line on the functions.php, I suggest you to install the Plugins I recommended above. Because, if you use the line on main theme instead of the child theme, this code will be removed whenever you update your theme. If you use the plugins, it will be easier for you to deactivate whenever you need.
This command helps to remove all the caches from the server.