Right compression settings to save JPG images for WordPress

Basically, there’s no “right” compression value that suits all the images since not all the images have the same subject. The finer and sharper the details in the photo the more you’ll have to lower the quality to get a smaller size. The trick is trying to set the lower quality setting possible (higher compression level) just before the artifacts start being noticeable by the eye, in the final media.

You can’t fine tune the compression on an image if you are not seeing it at the final size on the final media. Printed media lowers compression artifacts when linear halftoning is used, low resolution screens maximize artifacts, re-sampled images help or worsen them… so looking at the final size on the final media is recommended when saving jpg images.

What’s the right setting for saving images for WordPress?

Since WordPress is a web platform, the images need to be saved to be seen on a screen. So there’s no need to ensure the image being seen in different sizes or media, but one: real size, i.e. 1:1 (that means 1 pixel of file to one pixel of screen), on a screen at least 96ppi, as the standard for LCD pixel pitch. That said, the best compression setting is: The lower you can set before your eye start seeing any artifact.

There’s no way to set compression/quality settings in a single basis in WordPress, yet, so you’ll have to save your images in some photo editor, at the final size, and prevent WordPress re-compressing them.

Watch out for WordPress re-compression

Keep in mind WordPress generates exact pixel sized images to place them into posts as per the media settings specified in your admin panels, when you use any size other than “full” size. That means that your photo is being re-sampled, and re-saved, using default compression (or desired setting when using the above PlugIn) if it is bigger than the final size you chose.

The right settings explained above require you to “see” how low you can go with the quality value for each individual photo and that’s something you can’t do in WordPress. If you want to take advantage of the individual compression adjustment you need to re-size the images yourself BEFORE or at saving time from your own image processing application, NOT after saving nor leaving the photo at original size. Otherwise WordPress will take your optimized image and will re-size it, ruining any individual optimization you have done.

The original photo you could link your thumbnail or column-sized versions to, will remain untouched though, but that’s not something you would care about, since those are not read every time with your blog but just when some get interested in it.

How do I make my images smaller?

1. First of all, try not to start from already-compressed images. JPGs have artifacts and GIFs have noise. Start from the original when possible.
2. Smooth fine detail and grainy areas if they are not part of the main subject.
3. Reduce graininess whether possible
4. Control the JPG setting WordPress uses when creating thumbnails with some PlugIn like JPG Image Quality
5. Consider saving images as GIF when images have few colors, e.g. all red-ish colors, all blues, etc.