Why images/photos after being uploaded to my wordpress site get slightly blurry?

I am trying to figure out the problem stated in the title. Every image/photo I upload to my wordpress site gets slightly blurry. I format them according to my wp theme requirements, however after the image is processed by wordpress and I open the site in a browser I is slightly blurry. This is specially noticeable in Firefox browser.

What am I doing wrong?

I use photoshop to export images for web and on my computer they look just fine. I tried exporting them directly from Illustrator and the same scenario occurs. So I believe its on wordpress side.

Thank you!

Solutions Collecting From Web of "Why images/photos after being uploaded to my wordpress site get slightly blurry?"

Actually WordPress reduce quality of image when you upload it via media uploader. WordPress has built in compression for JPG images. Whenever you upload an JPG/JPEG image to WordPress media library, WordPress will automatically compress your images to 90% of the original quality, this is intended to help your pages load faster and keep file sizes smaller.

You can disable image compression and force WordPress to keep maximum quality images with this function.

// Set image quality
function my_image_quality( $quality ) {
    return 100;
}
add_filter( 'jpeg_quality', 'my_image_quality' );
add_filter( 'wp_editor_set_quality', 'my_image_quality' );

Normally this might due to some discrepancy from default set values for image in functions.php in wordpress and check whether any default values is set for the images in that file. You also can set it manually in function.php file as below.

add_theme_support('post-thumbnails');
update_option('thumbnail_size_w', 200);
update_option('thumbnail_size_h', 200);
update_option('large_size_w', 650);

add_image_size( 'my-thumb', 400, 8888 ); and add_image_size( 'my-thumb', 250);