I would probably do this manually but if you are looking for a plugin solution:
https://wordpress.org/plugins/png-to-jpg/
Related Posts:
- Restricting users to view only media library items they have uploaded?
- Programmatically adding images to media library
- Add image size where largest possible proportional size is generated
- Uploaded images don’t show in Media Library if there are special characters in IPTC Keywords
- Rename files on upload
- How to set the default embed image size
- Remove title attribute from images
- How do you modify the HTML output of a Gallery item (using the gallery shortcode)?
- WP 4.4 aspect ratio with responsive image
- Add CSS class to every image
- Prevent Width and Height Attributes in Image Tag Output
- How to associate an image with a term taxononmy and publish it on frontpage?
- copy attachment title to description and alt text
- add data-attribute to all images inside the_content()
- HTTP Error when trying to upload image
- Media sizes aren’t being created – server config?
- Removing Title Tag from Thumbnails
- WordPress login page logo customization
- New image size option not showing
- Make alt text required when setting a featured image
- How can i use wp_get_image_editor for image resizing
- Gallery images stored elsewhere (preferably Google Drive)
- WordPress gallery previous/next buttons showing all media library images
- Images not showing after moving site (but path id OK)
- Best way to strip character entities (%20 etc)
- 3.5 media.editor: what is the event listener for choosing an image?
- Display latest 12 images from media library
- Show featured image option not in screen options
- How to set a contact forms total size limit
- Get thumbnail url of custom meta image?
- SEO – Media File Name Updating
- All Images on wordpress site broken
- Multiple images in one attachment page
- How to keep WP from recompressing Full Size images
- How to get the url of an Image with id
- Missing a temporary folder.error when image is uploaded in admin Set temporary Directory – WordPress 5.2.2
- Hero image cropped at different dimensions
- Broken Images until Page Refresh
- How to add an image to a custom url?
- Get image from parent category
- Images attached to posts from library link to 404 error page
- Images not displayed when moving site to local
- Caption and title in img alt tag are the same?
- fetch images and videos
- Facebook og:image issues after https change [closed]
- How to use Facebox in WordPress theme?
- Mass crop images: Landscape images -> Portrait images
- How to display title of attached image in post?
- Getting thumbnail of uploaded image
- Display image for first sticky post only
- Get all image IDs from the Media Library
- How to redirect homepage to actual URL?
- Can’t add image to site via php
- Is it possible to enable the ‘Link To’ field under ‘Attachment Display Settings’ for a Featured Image?
- Save Image in wp_options-Table
- Can I register a new thumbnail size and have it be an option in “Add Media”?
- Is it possible to get feature image url (full-size) from an image url of smaller size?
- How to make Custom Loop not crop featured images?
- How to add “alt” attribute for image during upload at WP front-end?
- Get Original Dimension Featured Image on the homepage
- WordPress keeps resizing my 947×947 image down to 500×500 (full-size option)
- Excluding post thumbnail from the attachment.php when using wordpress gallery
- Featured Image Thumbnail size on Twenty Ten Archive Page
- How do I display the featured image from an image gallery using a reference in code? (example within)
- attach several images to post + gallery
- caption shortcode inserts blank paragraph
- How to change background slider image when hovering on text?
- Widget Style – Icon Type
- WordPress Problems
- Built-in image lazy loading: Does it come with a polyfill for older browsers?
- WordPress PHP custom function is causing 500 Internal Server Error Connection Timeout
- SQL: How to find all attachments that are not used in any posts/pages/custom_post_types
- How to trigger “wp_handle_upload_prefilter” filter when uploading an image programatically?
- How to add element to the list of adjacent images?
- Responsive Images – Defining
- Why do images inserted in the post content via the_content() go off the max-width?
- WordPress Javascript displaying an image Question
- Broken images in media library
- Using a full-width hero image that can be changed in the dashboard by a user
- Resize External Image
- Fatal error: Allowed memory size in PHP when allocating less
- Resized images not working – 404
- Declare global variable that can be used on other function
- Background image call problem
- How to replace all images within exported xml files to demo.jpg?
- Black and White Thumbnail in WordPress Gallery
- How to specify image width and/or height attributes for images uploaded using WordPress uploader
- How to change default image rename?
- Saving a post, content filtering and user levels
- Upload unnattached image from frontend
- Link images to post
- Image attachement management – a philosophical question
- How to extract specific image meta for all images?
- *box for images displayed as a post’s [gallery] [duplicate]
- Getting top Image From the Gallery and printing out a thumbnail with Exact Dimensions
- How to get WordPress to resize images for srcset?
- How to give path to image in wordpress?
- Edit multiple posts featured image
- Make Jetpack CDN to filter/ignore images based on SRC [closed]
- images map on website not working