Intermediate Masking/Overlaying

13th December | Tutorial

Let’s explore the masking and overlaying feature in more detail. We will see how masks and overlays can modify a photo’s look, and along the way, we will be creating some masks and overlays of our own to achieve some interesting effects.

Basic knowledge of using Photoshop or other graphic editing program is assumed, which is needed for creating the masks and overlays. Masks and Overlays are graphic files with an alpha channel to store the transparency information for each pixel.

Now, let’s start with a photo. Here is one taken of me and my buddies on a bike ride:

Original photo

I’ve changed the zoomed value to reveal the greenish-blue background. I’m gonna add to the slide background an image of a notepad:

Photo on notepad

Now for the fun part. Here’s how a mask works: when applied to a photo, the program multiplies the pixels of the photo with that of the mask to create the output. In simpler terms, regions on the photo corresponding to white areas on the mask will be visible, while those corresponding to transparent mask area will be invisible. So for example, if I have an ellipse mask like this (the hatch-patterned is from the empty background, which indicates transparent region):

Ellipse Mask

applying it to the slide (click on the “…” button and locate the mask graphic file), we’ll get this result:

Slide with ellipse mask

See how the background notepad image shows through the transparent region around the ellipse? Note that the name of the mask file must end with a “_MASK”. The mask graphic file can be in any format which supports an alpha channel. In this case, I’m using a png file with transparency.

We can have a semi transparent photo by having a translucent ellipse:

Ellipse Mask, 50%
and here’s how it will look:

Translucent Ellipse Mask

For this slide, what I want is a jagged irregular edge for the photo. This is the mask that I have created to do this:

Irregular Mask

Setting this to the slide, we have this:

Photo with irregular mask

Next, let’s look at overlays. Think of overlays as transparencies. When an overlay is set to a slide, the program simply stacks it on top of the slide, so in transparent regions of the overlay, the slide underneath will show through. I have created the following overlay of a tire mark for my photo:

Tire mark overlay

Now setting this to the slide, we get this result:

Slide with overlay

Pretty cool isn’t it? Now what if we want to apply BOTH an overlay as well as a mask? There is only entry for 1 file in the “Overlay” tab. Well, most masks and overlays are meant to be applied together as a set, and one usually doesn’t get applied without the other. Taking advantage of this pairing, MemoriesOnTV uses a naming convention to specify a set of associated mask and overlay: by using the same name for both files, extended with a “_MASK” at the end for the mask file.

Using our examples above, say we want to apply the irregular mask together with the tire mark overlay. So we’d name our overlay “tiremark.png”, and our mask “tiremark_MASK.png”. Once we have done that, we just need to set one of these in the “Overlay” field, and the other will be picked up automatically by the program. So here is our final result:

Final result

Note that the format of the mask and overlay files need not be the same. We can have a gif for a mask and a png for the overlay, e.g. coolpattern.png and coolpattern_MASK.gif (for some simple masks and overlays, the limited transparency support in gif suffices).

Masking and Overlaying will work for video clips too. Also, they work in exactly the same way on the buttons on disc menus as they do for slides (both single and multi-photo slides).

Hope this tutorial provides enough information to get your creative juice flowing. Do play around with these, and start creating interesting mask and overlay sets!

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