As noted in the comment below by cgaudreau, this will not work on iOS devices.
In the web design world, you might come across a site that has photos/images where if you click on the image, a larger version of that appears front and center, and the rest of the website is grayed out behind it temporarily...until you close the image to return to the webpage. This is commonly known as a "lightbox". The following are some related discussion threads I've found around the topic here in the Community:
Create a brand new content (wiki) page in your course.
Insert your photo/image into the page.
Grab the bottom-right corner of the image to resize the image so it is smaller ... making sure to keep the scale of the image relatively the same as the original (you should be able to hold the "Shift" key down while grabbing the corner to keep it scaled properly).
Add a line or two of blank space after the image you've inserted.
Switch over to the HTML view of your page, and paste in the following lines of code:
<div id="dialog_for_link1" class="enhanceable_content dialog">Bacon ipsum dolor amet pancetta cow...</div>
<p><a id="link1" class="Button Button" style="width: 20%;" title="This is the button description when you roll your mouse over it." href="#dialog_for_link1">Click to Learn More</a></p>
Click on the link to return to the "Rich Content Editor" view (leaving the HTML view for a bit). You'll see something like this:
Bacon ipsum dolor amet pancetta cow...
Click to Learn More<-- NOTE: this will be a button when you save the page.
Somewhere inside the "Bacon ipsum" text, click your mouse on where you'd like to insert the same image. Add the image the same way you did in Step #2. Remove any of the "Bacon ipsum" text that isn't needed.
Save your page. You will see your small image and then a button that says "Click to Learn More" (however, you could re-name this button to whatever you wanted).
Click on your button. You will see the full-size image in a pop-up (lightbox) window within Canvas. The pop-up (lightbox) might be a bit small at first, but you can grab the bottom right corner to expand the size of the box to see the entire image. (It sounds like you could also modify your global CSS file to tell the pop-up box (lightbox) to auto-fit instead of being restricted to a small view all the time. (vrs07nl, do you have that bit of code you'd be willing to post below?)
I've worked at MPTC since January 2001 as Web Specialist in the Instructional Technology department. Basically, I work with our Curriculum department to put courses into Canvas for our faculty. I enjoy playing disc golf, watching movies, playing video games, playing board/card games (Carcassonne, Settlers of Catan, Monopoly, Ticket to Ride, 7 Wonders, Forbidden Island, Forbidden Desert, Betrayal at House on the Hill, Splendor, Above and Below, Munchkin, and Exploding Kittens), reading, and being with family and friends. I help volunteer with our Sr. High Youth program at my church and also help with the soundboard and running slides for our Sunday services.
I am currently on my fourth Toyota Prius. The first (a silver 2004 2nd Gen) was victim to a flood that came through our area, and water got inside which ruined many of the electronics in it. My second (a magnetic gray metallic 2009 2nd Gen) was totaled in a rear-end collision. I totaled my 3rd Prius (a silver 2011) when I rear-ended someone by accident in town. I now have a 2019 Toyota Prius Limited...and it's awesome!