MatteLab
Tutorial
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This is just a tutorial page to inform you of what each control in the interface does.

First of all, what exactly does this program do? Well, this program takes an image (usually from footage filmed against a blue or green screen). Then, the user fiddles with the settings in an attempt to make a certain color, or range of colors, transparent so that the images can be placed, with only the desired subject showing, on top of other images.

The controls in this screenshot will be explained:

The File Menu (Upper Left): This is pretty straight-forward, you will find these options:
Load Image: This will load an image that you want to matte. Supported formats are jpeg, gif, tiff, and png.
Load Sequence: This will load a sequence of images and supports all the formats listed above. A sequence file is determined by it's first image (eg. sequence0001.jpg or sequence0000.jpg).
Render: This will render the image or sequence. Rendering is explained later.
Save and Load Filter Settings: These functions aren't implemented yet. You will get a popup if you select one.
Exit: This exits the program. Pretty obvious.

Preview Window (Right Side): The larger area that says "MatteLab" in the screenshot is the preview window. This shows the current frame with or without the changes.

Original and Modified Buttons (Below the Preview Window):
The Original button makes the Preview Window display the current frame without any changes. The Modified button makes the Preview Window display the current fram with the changes.

Start Rendering Button and Render Status Bar (Below the Original and Modified Buttons):
This button starts the rendering. Upon clicking this button, you will either be asked to choose a name then a directory to render your sequence, or to choose a file in which to render an image. When you render your sequence or image, MatteLab will filter each frame or the image and write it out in the specified directory or file. MatteLab can only write to png files. While rendering, the Start Renderin Button becomes a Cancel button if you need to stop a render. The Render Status Bar just displays the progress of a render if a sequence is being rendered.

Current Frame Scrubber (Almost at the bottom):
This just determines what frame to preview in the Preview Window. This is only effective if you are editing a sequence. The Current Frame also becomes the starting frame when the sequence is rendered.
Filter Settings
Hue and Hue Range (Left Side):
The Hue Slider is used to select which hue or color that should be matted out. The Hue Range Slider determines how close any color in the image has to be to the target hue, chosen by the Hue Slider, to be matted out. If the Hue Range is higher, than colors further from the target hue will be matted out.

Saturation High and Low (Left Side next to Hue Sliders):
These sliders determine the lower end and the higher end of the saturation range. Any amount of saturation, in the image that fit's within this saturation range will be matted out.

Lowest and Highest Values (Left Side under the Hue and Saturation Sliders):
Like the saturation sliders, these sliders determine the lower and higher bounds of the value (or brightness) range. Any part of the image that fit's within this brightness range will be matted out.

Note: A pixel in the image has to match all of the above criteria in order to be matted out.
Extra Processing Options (The AlphaBlur, Dynamic Matting, and Saturation Settings Tabs)
AlphaBlur

Alpha bluring is applied after the image has been filtered. It blurs the alpha channel. In other words, it blurs the amount of transparency in the image. Alpha bluring is used to get a soft blending around the subjects in the scene while keeping the subjects sharp. The Use Alpha Blur checkbox determines whether the alpha channel will be blurred after the image is filtered. The Blur Radius slider determines how much the alpha will be blurred. Increasing it makes the transparency softer, but increases rendering time significantly.

Dynamic Matting

Dynamic Matting behaves similar to Alpha Blurring, but can be used to control the edge softness of only a certain combination of settings (Hue, Saturation, and/or Value). Also, for Saturation and Value, the amount of softness can be weighted with the Target Saturation or Target Value Sliders. As parts of the image drift away from the target Value, Saturation, or Hue (determined by the Hue Slider discussed above under Filter Settings), that part gets matted out to a lesser degree resulting in a gradient from opaque to transparent. The Panel at the left is used to choose which property's settings to adjust. The Enable checkbox determines whether the active property (selected in the left Panel) should be dynamic. If the active property becomes enabled, it will remain enabled even when another active property is chosen. The Slope Addition changes how much effect the active property has. For Saturation and Value, the Target slider changes the weighting of the softness (described earlier).

Saturation Settings

There are only two options under Saturation Settings. The first option, Desaturate Transparent and Partially Transparent Pixels, will make any pixel that is not completely opaque desaturated or grayscale. This is useful for sequences, as a gray fringe is much less conspicuous than a blue or green fringe, especially when the subject is moving. The second object, Desaturate Transparent and Partially Transparent Pixels Based on Opacity, does what the first option does, but rather than making anything that is transparent grayscale, it will desaturate the pixels based on how transparent they are. In other words, if the given pixel is more transparent, it will become more desaturated.
That is all for this tutorial, if you want to learn more, just play around awhile and figure out what gets you the best results.


Tutorial and webpage by Evan Rosky.