LAYER CROPPING

Introduction.
It’s an often asked question: “What size of image should I use in my shows?”

The best answer is to use the original image at its default dimensions. Then, if you need to crop, for whatever reason, you can use either a mask or the crop feature. If you are NOT going to pan the image within the mask … and zoom in or out on the layer, the crop feature is your best bet.

ProShow’s crop feature is quite limited. So too is Photopia’s feature.

PROSHOW. If you know the target aspect that you want for the layer, you must be the one to come up with the associated crop dimensions. Up through the latest release of ProShow (v6.0.3104), there is no way to define an aspect and get associated crop numbers. However, it does allow you to enter any number you want and then to drag the crop region around the preview region.

PHOTOPIA. In Director/Creator, you chose the aspect ratio from the associated dropdown list. There’s 16:9, 3:2, 4:3, 21:9, 2:3, square, can custom. Note that there’s no 9:16, 3:4, or 9:21. That’s odd. Then, if you want to use custom, you need to so some math. Photopia uses percents as its answer to cropping. This is an added complexity for most of us.

Cropping Dimensions, How to do it.
When you do the math yourself, the resulting axis dimension value should be a number that is smaller than the original. If it is larger, you need to calculate the crop dimension for the other axis.

• Target axis. X-Axis = Tx. Y-Axis = Ty.
• Layer axis. X-Axis = Lx. Y-Axis = Ly.
• Cropped axis. X-Axis = Cx. Y-Axis = Cy.

If we set both of them as equal to each other : Tx/Ty = Lx/Ly
So, the target X-Axis corresponds to the layer X-Axis and the target Y-Axis corresponds to the layer’s Y-Axis.

So, to calculate the desired crop region, we need to search for the new width or new height for the layer. So to find the cropped width use the following equation:

FIND CROPPED WIDTH: Cx = Ly(Tx/Ty).

If the target aspect is 2:3 and the layer aspect is 4672:3104 then,

Cx = 3104(2/3) = 2069.33

Therefore, the 4672:3104 layer that is cropped to a 2:3 aspect has cropped dimensions of 2069:3104

For Photopia’s Director and Creator, we need another step. We need to divide the reduced axis pixel value with the original pixel value. In this example, that would be (2069.33/4672)*100. That provides a percent value of 44.29%. The other axis is 100(3104/3104) = 100%. Therefore, the initial crop is left = 44.29 and top is 100. Leave right and bottom at 0 and 100, respectively. Move the cropped region around as desired.

Note that if the cropped height had been looked for, we would use the following  equation:

FIND CROPPED HEIGHT: Cy = Lx(Ty/Tx)

When the layer dimensions are entered, this is the result:

Cy = 4672(3/2) = 7008.

Note that the layer’s original height is only 3104. You cannot crop (cut away) any part of a layer when the crop dimension requires a larger size than what the original layer has … it’s simply impossible!

SUMMARY. To find the cropped layer’s
• WIDTH for a given height, use this equation: Cx = Ly(Tx/Ty)
• HEIGHT for a given width, use this equation: Cy = Lx(Ty/Tx)

For Photopia’s Creator or Director, divide the calculated width (or height) value by the original value and multiply by 100. This gives you the left and top or right and bottom values for cropping.

© Copyright 2014-2020, Dale L Fenimore, FPVP 141217-1305, 200706