Abrar Ahmed

This plugin is particularly designed for developers so that they can easily upload images via URL.
Features of this plugin: 
1. You can give URL to this plugin then this will upload the image to WP and will return attachment ID. 
2. You can give the same URL multiple times but it will not upload an image each time, it will upload an image once and will return attachment ID each time when it is called. 
3. If image URL is change or size of the image on URL is different then just on that condition image will be uploaded to WordPress
It has some more functions too that will help developers for getting details about image and size as well.
<h3>Arbitrary section</h3>
The following features of this plugin are going to be defined for developer understandings.
<h3>A brief Markdown Example</h3>
Unordered list:
<ul>
<li>Function iUploadImageByURL This function is the basic function that can be used while upload image from URL. It will return Attachment_ID after creating an attachment from image URL. Image from URL will be uploaded once if URL and size of the image are same. If the same URL with the same size of the image given then already created attachment of that image will be uploaded.</li>
<li>Function iGetFileSize This function can be used to get the size of the image from URL.</li>
<li>Function sFormatSize This function will return measurement format size of the image.</li>
</ul>

URL Image Uploader

This function is a tool for developers to help them upload images from URL to the WordPress site.

gabrielmioni

GM Community Gallery allows WordPress users to administer a gallery and accept images from site visitors. It requires zero configuration to start using immediately.
There’s three basic parts to the GM Community Gallery: 
1. GM Submit Form: This is where your site visitors can upload images. 
2. GM Public Gallery: Where uploaded images are displayed. 
3. GM Community Gallery Admin: When you administer and make changes to uploaded images. Also (optional) settings!
To create a GM Submit Form on a WordPress Page: 
– Use the shortcode [gm-submit-form][/gm-submit-form]
To create a GM Public Gallery on a WordPress Page: 
– Use the shortcode [gm-public-gallery][/gm-public-gallery]
Once the GM Community Gallery plugin is installed, the admin panel is found in the beneath ‘Settings’ in WordPress Admin.
<h3>Features</h3>
<ol>
<li>Attractive public facing uploader allows site visitors to upload .jpg/.jpeg, .png and .gif images with a message. Submission data is validated and processed with Ajax. If JavaScript is disabled, a non-Ajax form is displayed instead.</li>
<li>Administrative tools the gallery administrator can use to edit/view image data and move images to ‘trash’ before choosing to permanently delete images.</li>
<li>Public gallery JavaScript lightbox that lets viewers navigate images and view image messages. On desktop the lightbox can be navigated with mouse clicks or keyboard. On mobile the lightbox is navigated by touch and swipes.</li>
</ol>
<h3>Gallery Admin</h3>
I. Gallery Options.
Configuration (like many good things in the world) is optional.
To access the the GM Gallery Options:
<ul>
<li>From the WordPress Admin Panel, hover or click ‘GM Community Gallery’ and select > ‘Gallery Options’</li>
</ul>
Here you can set the GM Community Gallery to do some things:
<ol>
<li>
Send Notification – If this is enabled, an email will be sent every time someone submits an image. By default this will be the email address associated with the WordPress administrator, but you can set a different email address in the ‘Notification Email’ field.
</li>
<li>
Max Image Size (kb): Specifies the maximum file size you want to allow. By default, GM Community Gallery will accept files up to 500 kilobytes. You can raise or lower that value here.
</li>
<li>
Images per page: Sets how many images you would like to display per page. GM Community Gallery includes a page navigation bar with the gallery. By default, the gallery will display 10 images per page.
</li>
<li>
Banned IPs: Folks stepping out of line? You may banish them by adding their IP addresses to this this textarea.
</li>
</ol>
II. Admin and Trash Galleries
When you click on GM Community Gallery from the WordPress admin panel, you’ll see both Admin and Trash galleries in the left navigation panel. Each includes an image count in the title.
<ol>
<li>Admin Gallery:</li>
</ol>
Here you can search for and navigate the images in your gallery. Percentage signs [ % ] can be used as wildcards (e.g., searching ‘Bill%’ will find both ‘Billie’ and ‘Billy’).
Clicking on an image will bring you to the gallery edit screen where you can review and make changes to image metadata (including Title, Submitter Name, Submitter Email and IP).
You can also both edit the message the image submitter included with their upload and post/edit a reply. Replies will be displayed in the Public Gallery lightbox and image view pages.
Multiple images can be selected and sent to ‘Trash’ either by individually clicking the checkbox for chosen images or using the ‘Select All’ checkbox (after which individual images can be de-selected).
<ol>
<li>Trash Gallery:</li>
</ol>
Once an image is in the Trash Gallery it will no longer be displayed in the Public Gallery. From here, you have the option to permanently delete an image and its associated meta data (including data about the submitter and any message/reply content).
If you have second thoughts, you can also move images back to the Public Gallery.
Both ‘permanently delete’ and ‘move back to gallery’ options are managed by clicking the checkboxes for images on which you want the action to apply and then clicking the ‘Submit’ button. Like the regular admin gallery, a ‘check all’ checkbox is available.
<h3>Attributions</h3>
<ul>
<li>Icon by faisalovers from the Noun Project</li>
<li>Banner art from Gallery of the Louvre by Samuel F. B. Morse</li>
</ul>

GM Community Gallery

The GM Community Gallery is a public gallery plugin for WordPress that allows site visitors to upload images.

URL Image Uploader vs GM Community Gallery