Image Import

Typically, the first thing we do with this slideshow program is to import an image. In general, you notice that, upon import, your image fits on the screen quite well. Often, you will not think a out it beyond that fact. What most do not realize is that ProShow automatically resizes the imported image for you so that really small or really large images fit on the screen just fine. The question is, why is this happening?

ProShow uses a representation (or metaphor) for a physical slide that it calls a slide (and often refers to as a frame when the slide is open for editing on the screen). This Photodex slide represents the film-based version of a slide that historically was created using camera film. The film was placed between two pieces of thick paper that had a rectangular section removed from their center. While looking through the hole, you would view what was on this film by shining light from behind it. Typically though, light was shined through this hole and the content of it was passed through a lens (to magnify it) and displayed onto a screen or wall. The slide itself was typically placed in a carousel that could hold 80 or more slides. The carousel was used on a projector that would then be used to display each slide, in turn.

ProShow’s technique more or less duplicates this approach with some added effects that come as the result of technology. Since ProShow is electronic instead of physical, all kinds of things are possible. Adding music or other sound to the slide itself adds a dimension most slideshows in the past never had (but, that’s another story). So is displaying multiple images on the same slide. In the old days, whatever was on the slide was all you got and that was typically a single photo. In this era of electronic images, we have considerable flexibility into what’s possible on a single slide. That includes motion effects, multiple images, multiple graphics, text, video, sound effects, and music. To do achieve this flexibility, however, ProShow must know something about the image ProShow imports onto the slide metaphor. The slide itself is fixed in size while the image itself might be of any size. So, upon import, ProShow reads the image’s width and height and then sizes it to the slide. This is called “normalization.” Once a correlation between the image and the ProShow slide is established, ProShow now has a basis for calculating the layer’s position and size (among other things). The method ProShow uses to establish this normalization is referred to scaling.

The slide is represented by the screen (or frame) and is defined by the show’s aspect ratio which is itself defined by the ratio of the show’s width to its height. It is often represented numerically, such as 16:9 or 4:3. These examples refer to a screen that is 16 units wide by 9 units tall and one that is 4 units wide by 3 units tall. It may also be referred to by a number representing the division of the width divided by the height. So, 16:9 is 16/9 = 1.778 while 4:3 is 4/3=1.333.

Screen Referencing
Figure 1 Screen Referencing

ProShow provides the following scaling options during import: Fit to Frame, Fill Frame, Stretch to Frame, Fit to Safe Zone, and Fill Safe Zone.  Each option is discussed below. Before getting into that however, I need to discuss a few things.
●    The ProShow screen works on percents (see Figure 1). The screen width and height are each 100% of the screen. Screen position is referenced from screen center such that 50% of the screen is on each screen center’s side. A normalized layer has at least two sides along one axis that are 100% of the screen along the same axis. If W represents the layer’s width, H represents the layer’s height, and Z represents the layer’s zoom, then when the
○    Layer and Show Width are the same: W=Z (Width is normalized).
○    Layer and Show Height are the same: H=Z (Height is normalized).
○    When one layer axis is normalized and the other is not, the non-normalized axis varies from the associated screen axis by an amount I refer to as the correction factor. This factor, F, is simply the ratio of the screen aspect to the layer aspect. So, Sx and Sy are the show’s x-axis and y-axis dimensions and Lx and Ly are the layer’s x-axis and y-axis dimensions, respectively, we get the following relationship:

F = (Sx/Sy)/(Lx/Ly)  Equation 1


PROSHOW’S SCALE OPTIONS
. Figures 2 and 3 are examples of what happens when a layer is scaled to the frame. Two common image sizes, 4:3 and 3:2 aspect, are scaled to a 16:9 slide. For the examples provided in the figures, the 16:9 screen aspect (16/9=1.778) is larger than the layer aspects of 4:3 (or 4/3=1.333) and 3:2 (or 3/2=1.50). When a layer’s two opposite sides are the same as the frame’s two sides, the layer is sized to 100% of the frame along the axis represented by those two sides. Those are the normalized sides. When the screen aspect is smaller than the layer aspect, the normalized axis is opposite of when the screen aspect is larger than the layer aspect. Obviously, when the screen and layer aspects are the same, both axes are normalized.

Fit To Frame. Refer to Figure 2. Layer resizing stops when the first two opposing sides reach their corresponding Frame sides.

  • For the given example, the layer’s height is 100% of the screen’s height. However, the screen to the layer’s left and right is unfilled. See ProShow Equations. The layer’s width (W) is defined by its zoom (Z) divided by the correction factor (F): W=Z/F.
Figure 2 Fit to Frame Example
  • 4:3 Example: How much screen is unfilled? Zoom=100%. The 4:3 layer’s F=(16/9)/(4/3) = 1.333. So, W= Z/F = 100/1.333 = 75, which means 100-75=25% is unfilled screen.
  • 3:2 Example: How much screen is unfilled? Z=100, F = (16/9)/(3/2) = 1.18519. So, W=Z/F = 100/1.18519 = 84.375. So, 100 – 84.175 = 15.625% is unfilled screen.

NOTE: When the screen aspect is smaller than the layer aspect, use Fill Frame scaling equations .

Fill Frame. Refer to Figure 3.  Layer resizing stops when the last two opposing sides reach the corresponding Frame sides.

  • Refer to ProShow Equations. For the given example, the layer’s width is 100% of the screen’s width at 100% zoom. However, the images extend beyond the screen frame. The layer’s height (H) is defined as its zoom (Z)  multiplied by its correction factor (F): H=ZF.
Figure 3 Fill Frame Example
  • 4:3 Example: How much of the image extends beyond the screen frame? F = (16/9)/(4/3)=1.333. H=100 (1.333) = 133.333. The amount of the layer that’s off-screen is 133.333 – 100= 33.333 (16.67 above and below the screen).
  • 3:2 Example: How much of the image extends beyond the screen frame? F = (16/9)/(3/2)=1.18519. H= 100(1.18519) = 118.519. The amount of the layer outside the screen is 100-118.519 = 18.519 (9.259% above and below the screen).

NOTE: When the screen aspect is smaller than the layer aspect, use Fit to Frame scaling equations.

Stretch to Frame. Layer resizing stops when all of its sides match the frame sides. That is, the layer is stretched until its sides match the show’s sides. Review Figures 2 and 3. Note that means the layer and show have the same width and height.

Fit To Safe Zone. A Fit To Frame variation. The layer fills the area defined by the Safe Zone Settings in the same way as Fit to Frame scaling. That is, the layer stops resizing when its first two sides reach two corresponding sides of the safe zone region. NOTE: When screen aspect is smaller than layer aspect, use Fill Safe Zone scaling equations.

Fill Safe Zone. A Fill Frame variation. The layer fills the area defined by the Safe Zone Settings in the same way as Fill Frame scaling. That is, the layer stops resizing when the last two sides reach two corresponding sides of the safe zone region. NOTE: When screen aspect is smaller than layer aspect, use Fit to Safe Zone scaling equations.

140525-0800 © Copyright Dale Fenimore, All Rights Reserved
140528-0645

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