Using Differently Scaled Masks and Images Together


Recently, I came across someone asking for some unique help. He was using two different scales in the same mask set: fit to frame for the mask and fill frame for the masked layer. He had two different mask sets that displayed the same image. One mask set was smaller than the other. The information concerning size and position of the smaller mask set were known as was the size and position of the larger mask set’s mask layer. What he wanted to know was how to determine the size and position of the larger mask set’s image layer such that it displayed the smaller mask set’s image exactly the same … just at a larger size. This is what is being attempted. Note that the larger image is positioned exactly the same as the smaller image in Figure 1. But, Figure 2 shows that the image in the small mask set is offset slightly from it’s mask’s position.

The Result
FIG 1. Large Image Size and Position Found from Size and Position Info for Small Mask Set and Large Mask.
Fig 2. Basic Relationships between the images and their masks. The Images are offset from mask layer centers. Given the position of the Small Image relative to its mask, how is the large image accordingly positioned to its mask?

The size and position of the two mask layers and of the small mask set’s masked layer are known. So, how do you find the appropriate size and position of the large mask set’s masked layer such that it presents the same portion of the image as that of the small image?

Both images are masked in such a way that only a portion of the actual image is displayed. However, each display exactly the same area. (See Figure 2 for the relative position of the images to their masks).

There are two issues associated with this scenario.
Issue 1: What zoom value for the larger image is required such that it scales to its mask as the smaller image layer scales to its mask?
Issue 2: How is the larger image positioned within its mask to match the smaller image’s display within its mask?


The first requirement is to identify what setup is being used and exactly what information is being sought.

MASK, Small
Aspect = 800:1200; Scale = Fit to Frame;
Zoom = 25, 25; Pan = -35, -30

IMAGE, Small
Aspect = 800:1200; Scale = Fill Frame;
Zoom = 12, 12; Pan = -36, –29

MASK, Large
Aspect = 800:1200; Scale = Fit to Frame;
Zoom = 60, 60; Pan =25, 10

IMAGE, Large
Aspect = 800:1200; Scale = Fill Frame;
Zoom = ?, ?; Pan = ?, ?

So, what is being sought are the larger image’s zoom and position settings. Since the mask and image layers possess different scales, the sizing for each is a bit of a problem to figure out (as you may have discovered). Most of us would have no clue how to address this kind of situation. Mainly that is because it is not a situation that appears very often. Most of those who are considered experts have probably run into this situation at one time or another. However, we usually just make sure our workflow avoids this kind of situation. That’s simply because when the layer and mask share the same scale and aspect, calculations for size and position are considerably simplified.

Sometimes, however, a situation arises where there is a need to use different scales at the same time. When that happens, the following information may be of assistance.


1) EQUATIONS. The following link is to a webpage that contains equations that are very important to addressing the described situation.

These are the relevant equations for all layers at any aspect. The equations of interest here are those for the layer’s width and height. You need that information (it is important). ProShow does not, at this time, provide this information anywhere. If it is needed, manual calculations are required.

2) PROSHOW SCALES. This article may be of interest:

(read all of sub-articles to that link). Of interest because it explains how a layer is scaled (at least to my understanding). It forms the basis of understanding much of how ProShow does its magic.

3) OTHER TUTORIALS. These tutorials may help too:

They cover a number of issues on how to use ProShow.


With the specific setup given above, the first thing to do is to find each layer’s width and height. Use the equations link above to find the appropriate equation to use.

1) Find Each Known Layer’s Width and Height.
The width and height values are calculated for a 2:3 aspect layer:

1a) For a zoom of 25, 25 and a scale of fit to frame: 9.375, 25.
1b) For a zoom of 60, 60 and a scale of fit to frame: 22.5, 60.
1c) For a zoom of 12, 12 and a scale of fill frame: 12, 32

2) Find the Width and Height of the Unknown Layer.
Once the width and height for each of the three given layers above has been calculated, the width and height for the fourth (and related) larger image layer can be calculated.

2a) Fit To Frame and Zoom. A layer using a fit to frame scale and which has an aspect that’s smaller than the slide’s aspect has a height controlled by the Zoom-Y. That is because the layer has been normalized along the vertical axis (that is, the layer at 100% zoom has the same height as the slide).
2b) Fill Frame and Zoom. For the same layer that uses a scale of fill frame, the layer’s width is determined by Zoom-X. In this case, the layer’s width at 100% zoom is 100% of the slide’s width. This is important information to know.
2c) Change in Width, Small Mask Set. Knowing the information provided in the above paragraphs, the next step is to determine the change in width for the image layer relative to its mask layer. We know that the small image layer has a width of 12 while its mask layer has a width of 9.375. The image layer’s size difference from its mask is found by the following:

(Image Width – Mask Width)/Mask Width = change in size

After substituting the actual width values into the equation, we arrive at the following:

(12 – 9.375)/9.375 = 0.280

2d) Zoom for Large Mask Set. The information just calculated allows us to find the larger image’s size. We know that the large mask has a width of 22.5 and now we also know the amount of proportional change that will give us the larger layer’s width. So, the following relationship is used:

Mask Width + (Mask Width times change amount) = Layer Width

Now, the mask layer’s width and the just calculated change amount are substituted into this equation. That gives the following:

22.5 + (22.5*0.28) = 28.8

Since the layer width is determined by the layer’s zoom setting for a fill frame scaled layer that has an aspect that is smaller than the slide’s aspect, 28.8 is the image layer’s zoom setting as well. So, that gives the large image a zoom of 28.8, 28.8.

2e) Large Layer’s width, height, and zoom. When we know the large layer’s zoom values, we can substitute this information into the equations to get the layer’s width and height. The values we were missing are now known as follows:

Zoom = 28.8, 28.8; Width and Height = 28.8, 76.8

3) Position Settings For the Large Image Layer.

3a) Default Position. As for the pan settings, each layer of the mask set can share the same pan values despite having different scales. That is because the position, or pan setting is referenced from layer center, always.
3b) Offset Position. When the smaller image layer is offset from its mask’s center, what is the new associated pan setting values for the larger image layer relative to its mask layer’s position? The answer is dependent upon the change in size between the smaller and larger image layer’s. So, we need to know the change is zoom setting for the layer’s width or height. Because the two layers have already been normalized to the slide and they share the scale, we just calculate the change in size for each. This then correlates to a change in the scale of the pan setting as well.
.    3b1) We know the small layer’s width and height is 12, 32 and the larger layer’s width and height is 28.8, 76.8.  The width difference then is 28.8/12 = 2.4. For the height, it’s the same result: 76.8/32=2.4. It means that for every 1% change in the small image layer’s offset from its mask layer’s position, there is a 2.4% change in position of the larger layer’s offset from its mask layer.
.     3b2) With that in mind, the offset of the small image layer from its mask’s position is -36 – (-35) = -1, -29 – (-30) = 1, or a change of -1,1. Therefore, the offset of the large image layer from it’s mask is 25 + (2.4*(-1)) = 22.6, 10 + (2.4*1) = 12.4, or a pan setting of 22.6, 12.4.


The small mask set information:
MASK: Aspect = 800:1200; Scale = Fit to Frame; Zoom = 25, 25; Pan = -35, -30. Width, Height = 9.375, 25.
IMAGE: Aspect = 800:1200; Scale = Fill Frame; Zoom = 12, 12; Pan = -36, –28; Width, Height = 12, 32.
The large mask set information:
MASK: Aspect = 800:1200; Scale =Fit to Frame; Zoom = 60, 60; Pan = 25, 10; Width, Height = 22.5, 60.
IMAGE: Aspect = 800:1200; Scale = Fill Frame; Zoom = 28.8, 28.8; Pan = 22.6, 12.4; Width, Height =  28.8, 76.8

This is a Demo using 2 Different Scale types:

Have fun exploring!

© Copyright 2014, Fenimore’s PhotoVideo Productions, LLC. All Rights Reserved



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