In image occlusion, you generate flashcards from an image by hiding parts of it behind an opaque box on the front side, then revealing the hidden portion on the back side. It's like cloze deletion, but for images.

Image occlusion can be useful for any subject, but is especially helpful for visual-heavy topics like anatomy, chemistry, data science, or geography.

Image occlusion is a Pro feature. You can create image occlusion flashcards from up to 5 images on a free plan, so you can try it out before committing to the Pro plan.

Before creating an image occlusion flashcard, you'll need to add an image to your notes. Or, if you have the URL of the image handy, you can use /ioc (insert image occlusion) to add the image and start an image occlusion in one step.

Otherwise, Ctrl+click on the image you'd like to create cards for (Cmd+click on a Mac), or click the image flashcards button that appears in the upper-right corner of the image when you hover your mouse over it. (On a mobile device, tap once to show these options.)

This opens the image in a window where you can begin selecting what parts of the image you want to occlude (hide from the front of the flashcard). Click and drag to cover the area you want to test yourself on. You can occlude any rectangular area you want, and add as many different occlusions as you want.

Occlusions are rectangular by default, but if a rectangle isn't quite right for what you're trying to hide, click the image occlusion tool in the toolbar and pick a different shape from the list.

If you want to hide all the labels in a diagram, RemNote can try to automatically create the occlusions for you – click the Generate Cards with AI button on the upper-right toolbar.

If the boxes aren't quite perfect, you can edit or merge them (see next section) after creation.

Generating cards with AI uses AI credits; the amount used depends on the image. As a side benefit, RemNote also recognizes the text under each occlusion as part of the same process, which means the Type in Labels in Queue option (covered below) can check your typed answers against the actual text in the image — even if you haven't added a back-side label yourself.

If a rectangular box isn't quite the right shape for what you want to hide, switch to the image occlusion tape in the toolbar. It lets you cover areas more freely, with a tape-like stroke.

The tape tool works everywhere image occlusion does: regular images, PDFs, and handwritten documents. Tape occlusions support most of the same options as regular occlusions: you can rotate, merge, and set occlusion areas. (Labels aren't currently supported on tape occlusions.)

By default, each occluded area generates its own card, but you can merge occlusions so that multiple areas will be hidden on the same card. The letters on each occlusion indicate which ones go together; each letter corresponds to a single card that will be generated.

To merge, hold Shift and click on multiple sections (or use the checkboxes that appear next to the items when you start selecting them), then press the Merge button on the toolbar.

If you change your mind, you can split merged occlusions back into their own cards by selecting them and pressing the Split button on the toolbar.

You can add additional details to image occlusion cards as labels. To add a label, click on the occlusion you want to label, then the … button, then Label Front of Card or Label Back of Card, depending on whether you want the label to appear on the front or the back of your card. Front-side labels are useful for providing prompts or hints; back-side labels are useful for reminding yourself of mnemonics or additional context.

In this example, we show the first letter of the nucleotide being tested so we can remember which one it's asking for without memorizing the colors in the diagram.

Sometimes the part of the image you want to hide isn't at right angles to the image. You can draw an occlusion and then rotate and move it to neatly cover the appropriate area using the circular rotation point at the top of the occlusion.

By default, an image occlusion card shows the entire image when it appears in your queue. Sometimes that's not what you want - maybe another part of the image gives away the answer, or the image is large enough that you'd rather only see the relevant region while practicing.

For any occlusion, you can define an occlusion area: a region of the image that will be shown when you're tested on that card, with the rest cropped out. Click on the occlusion, select Set Occlusion Area, then draw a box around the part of the image you want to keep visible during practice. Each card can have its own area, so different cards from the same image can focus on different regions of a large diagram.

In the example below, we want to remember the name and location of the femur, but the full skeleton image is too large to comfortably see the occlusion in the queue. Setting an occlusion area around the leg bones means only that region appears when the card comes up.

There are several more options on the settings menu (gear icon) in the upper-right toolbar of the image occlusion interface.

If you have a back-side label (see the Labels section above) for an occlusion, RemNote will show a type-answer box asking you to fill in that label.

If there is no back-side label but you used Generate Cards with AI, RemNote will read the text under the occlusion and use that as a back-side label for purposes of this option. (A back-side label, if any exists, will override the automatically determined text.) For more on type-answer cards in general, see Typing in answer.

You can create a single card that asks you to answer all of the occlusions in a specific order, like a list-answer card. In many cases, this is a great way to get extra practice and improve your memory.

This setting offers three options:

When this option is enabled (either Test boxes in sequence or Both), small numbers will appear above each occlusion in the editor. You can click on these to change the order in which the occlusions appear (they start in the order in which you created them).

When an image occlusion card generated from this image appears in your flashcard queue, RemNote will automatically zoom in to it, as if you had clicked on the image. This is useful for very large images that would otherwise be difficult to read.

You can either show everything on the front side of each card except the current occlusion (the default behavior), or hide all occluded portions on every card (showing the item(s) you are supposed to answer in this particular card in blue and the others in gray).

In the example below, Hide All, Test One is enabled. We're being tested on the first occlusion (shown in blue), while the other occlusions on the image are hidden in gray.

With the setting turned off, only the occlusion we're currently being tested on is covered. The rest of the image is fully visible.

Even with Hide All, Test One enabled, you can reveal the other occlusion boxes on demand, for example, if you're stuck and want a hint. Open the card full screen by clicking the image, then click the eye icon in the upper-left corner. (Click it again to hide the occlusions.)

RemNote will save your choice here and use it for the next card you create, so if you create many cards in a row that belong in one mode or the other, you don't have to keep changing it on every card.

Image occlusion isn't limited to standalone images. You can also occlude parts of PDFs (like textbook diagrams or slides shared by your professor) and handwritten documents (like notes you took during a lecture), directly inside the document itself.

To get started, open the drawing tools in the toolbar at the bottom of the PDF reader or handwritten document. From there, occlusions work the same way as they do in an image: you can create them with a standard occlusion box or with the image occlusion tape, and all the same options apply (rotating, merging, labels, occlusion areas).

There's one nice perk to cards generated from PDFs and handwritten documents: when one comes up in your flashcard queue, RemNote loads the document the occlusion is in along with it. That means you can scroll back through the document right from the queue if you've forgotten an answer and want to revisit an earlier page - no need to leave practice to find the source.

Charts, graphs, models, diagrams, and flow charts make excellent image occlusion material. If you don't have the right one, consider making your own and uploading it to RemNote!

Image occlusion cards are also a fast way to test yourself on the contents of tables you might find in a textbook or on a website: grab a screenshot of the table, paste it into RemNote, and then generate image occlusion cards.

Image occlusion is an easy way to study important equations in subjects like chemistry, physics, or math. Snip the equation you need, upload it as an image, and start occluding!

(Note that you can also type equations directly in RemNote. But the image occlusion method can come in handy if you don't want to retype a long, complex equation whose LaTeX source you lack.)