Final Image Sizes??

Jun 08, 2017

Changing the output quality of a course doesn't seem to change the size of the individual image files within the mobile folder -- they remain the same size regardless of if I publish at 100% or 50%. What is actually being compressed in Storyline to lower the overall size of the zipped package?

On average, how big are the image files in your courses upon publish?

18 Replies
Daniel Sposato (Philly)

Hey Ashley, not sure exactly what SL does but I'd imaging it lowers the pixel count on the pallet of the images.

Did you adjust your image compression with the Publish Quality settings? Clicking the Publish option and then under "Properties" toward the bottom click on "Custom optimization" next to Quality. The following image shows you the compression options you are presented with if using SL2:

Ashley Schwartau

Yes, regardless of what we select for Image Quality, the size of the images in the Mobile folder in the Output folder remain the same (seemingly full resolution). See the attached images -- one is from publishing the image quality on 10% and one is from publishing the image quality on 60%. Literally the same final image size. 



So I'm trying to understand how the image compression works and what is actually being made smaller, especially as we have clients complaining about the size of the images. (Now we have gone in and shrunken all of the images post-publish using and got them all down to under 500 kb but they are STILL saying the "huge" images are spiking bandwidth, so I'm trying to understand better how images are loaded in a course, how Storyline compresses images, etc.)

Alyssa Gomez

Hi Sally,

The reason you're seeing increased image sizes is because the resolution at which we publish PNG files has changed for the HTML5 player in Storyline 3 and Storyline 360.  We'd be happy to take a closer look at your file if you'd like us to compare the increased file size after publishing. You can send it straight to our Support team by clicking here!

Jordan Best

I've been comparing the output files of my SL courses with the source files, and noticed that sometimes SL converts JPEGs to PNGs during publishing. This happens with some files and not others; in one case, it converted every JPEG to PNG.

Also, in almost every case, the output PNG file is larger than the source PNG file.

I was wondering if anyone knew what method SL uses to decide when to convert JPEG to PNGs and why PNGs in the output are larger than their source? Very frustrating for bandwidth / file size reasons.

Jordan Best

The issue with this appears to be that any time an image is cropped in SL, SL converts that image to a PNG and does a very poor job compressing it. I have numerous images I crop in SL to make smaller in pixel count, but when published, they are almost always larger file sizes than the original uncropped images.

Is there a fix or a way for SL to handle image cropping better? It's really inefficient to go through all the images after publishing to shrink them, and also bad for bandwidth reasons to have these unnecessarily large files.

Rachel Grzymkowski

Hello. I'm having a similar problem with SL3 courses playing slowly. I've reduced all the image sizes to below 1MB but when i publish to LMS and look at the Mobile folder, i notice that SL3 has increased the image size to almost 5x what it should be. How do i make it stop?

I should note that we are running SL3 version 1.49.24347.0 because our LMS was having problems with the more recent versions. Publish is scorm 2004 - 4th

Ashley Terwilliger-Pollard

Hi Rachel,

It sounds like you're using the latest update of Storyline 360 actually, as we're on version 49 now!

As for the sizes your seeing, our image compression settings will only impact JPEGs, not PNGs. That being said, I wouldn't think that you should experience such a drastic file size increase. I'd love to have our team take a look - as they may be more familiar with those changes than I am! Are you able to connect with our Support Team to dig in on next steps?