IBM Visualization Data Explorer User's Reference

Overlay

Category

Rendering

Function

Overlays one image with another.

Syntax

combined = Overlay(overlay, base, blend);

Inputs

Name	Type	Default	Description
overlay	image	none	overlay image
base	image	none	base image
blend	scalar, vector, field, or string	.5	0: for base image only 1: for overlay image only

Outputs

Name	Type	Description
combined	image	combined image

Functional Details

overlay	is the overlay image.
base	is the base image under overlay.
blend	determines how the module combines the two images and what the output image will be. If the parameter is: a scalar value: the resulting image (combined) is equal to ((1 - blend) × base) + (blend × overlay) a vector or string: this value will be interpreted as an RGB color. The combined image is the base image except for the pixels where the base image is equal to blend. These pixels will be taken from the overlay image. This specification allows you to perform chromakeying. Two pixels are considered to have the same color if the corresponding component colors (i.e., red, green, blue) of one are each within 0.1% of the other. The blend can also be specified (in a string) as one of the standard X Window System** colors (see Color). a field of position-dependent data: each data value in the field is used as a blending value to overlay the two pixels (one from each image) corresponding to that position. That is, the blending is pixel by pixel. The "blending" field must have a grid that is compatible with both the overlay and the base image. The blend values in the field must be scalar values between 0.0 and 1.0.

Notes:

1. The images base and overlay must be the same size and have the same grid positions. The "colors" component must be dependent on "positions." The base and overlay images must both have the same partitioning (or none).

2. To add two images together, or subtract one from the other, use the Compute module. First mark the "colors" component in each image (with the Mark module), then, use Compute to perform the desired operation on each. Finally, use Unmark to return the modified data to the "colors" component.

Components

Modifies the "colors" component. All other input components are propagated to the output.

Example Visual Program

UsingOverlay.net

See Also

 Arrange,  Color,  Compute,  Display,  Render

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