Layered image rendering

• US 20020145615A1
• Filed: 04/09/2001
• Published: 10/10/2002
• Est. Priority Date: 04/09/2001
• Status: Active Grant

• Current Assignee: DTN, LLC (TBG AG)
• Original Assignee: Weather Central, Inc. (The Weather Co. LLC)
• Inventors: Moore, John S.
• Granted Patent: US 6,856,323 B2
• Time in Patent Office: Days
• US Class Current: 345/629
• CPC Class Codes: G06T 15/503 Blending, e.g. for anti-aliasing
• CPC Class Codes: H04N 5/272 Means for inserting a foreground image in a background image, i.e. inlay, outlay

Abstract

A method for creating a rendered scene that is composed of two or more RGB image layers that can be composited at a later time. The resulting composition will appear the same as if it were rendered all at the same time. The elements of a foreground image layer scene are rendered separately over a black background and a white background. The RGB components for each pixel of the foreground image layer scene rendered over the black background are combined with the RGB components for each corresponding pixel of the foreground image layer scene rendered over the white background to form a rendered foreground layer. The foreground layer may be combined with a background image layer in a conventional manner, possibly with additional material added between the background and foreground image layers.

Claims

1. A method for rendering an image layer scene, comprising the steps of:

(a) defining a scene of image layer elements;

(b) rendering the elements of the image layer scene over a black background to obtain RGB components for each pixel of the image layer scene rendered over black;

(c) rendering the elements of the image layer scene over a white background to obtain RGB components for each pixel of the image layer scene rendered over white; and

(d) combining the RGB components for each pixel of the image layer scene rendered over black with the RGB components for each corresponding pixel of the image layer scene rendered over white to form the rendered image layer scene.

2. The method of claim 1 wherein the step of combining the RGB components for each pixel of the image layer scene rendered over black with the RGB components for each corresponding pixel of the image layer scene rendered over white includes the steps of, for each corresponding pixel of the image layer scenes rendered over black and white:

(a) determining an alpha value for the pixel as one plus the value of a color component of the pixel from the image layer scene rendered over black minus the value of the same color component of the corresponding pixel from the image layer scene rendered over white;

(b) setting all of the RGB color component values of the pixel to zero if the alpha value for the pixel equals zero;

(c) otherwise setting the RGB color component values of the pixel to the corresponding color component values of the corresponding pixel from the image layer scene rendered over black divided by the alpha value for the pixel.

3. The method of claim 2 wherein the step of determining an alpha value for the pixel includes the step of determining the alpha value for the pixel as one plus the value of a red component of the pixel from the image layer scene rendered over black minus the value of the red component of the corresponding pixel from the image layer scene rendered over white.

4. A method for rendering a multi-layer image, comprising the steps of:

(a) rendering a background image layer;

(b) saving the background image layer;

(c) creating a foreground image layer scene of foreground image layer elements;

(d) rendering the elements of the foreground image layer scene over a black background to obtain RGB components for each pixel of the foreground image layer scene rendered over black;

(e) rendering the elements of the foreground image layer scene over a white background to obtain RGB components for each pixel of the foreground image layer scene rendered over white;

(f) combining the RGB components for each pixel of the foreground image layer scene rendered over black with the RGB components for each corresponding pixel of the foreground image layer scene rendered over white to form a rendered foreground image layer; and

(g) compositing the background image layer and the foreground image layer to form a multi-layer image.

5. The method of claim 4 wherein the step of combining the RGB components for each pixel of the foreground image layer scene rendered over black with the RGB components for each corresponding pixel of the foreground image layer scene rendered over white includes the steps of, for each corresponding pixel of the foreground image layer scenes rendered over black and white:

(a) determining an alpha value for the pixel as one plus the value of a color component of the pixel from the foreground image layer scene rendered over black minus the value of the same color component of the corresponding pixel from the foreground image layer scene rendered over white;

(b) setting all of the RGB color component values of the pixel to zero if the alpha value for the pixel equals zero;

(c) otherwise setting the RGB color component values of the pixel to the corresponding color component values of the corresponding pixel from the foreground image layer scene rendered over black divided by the alpha value for the pixel.

6. The method of claim 5 wherein the step of determining an alpha value for the pixel includes the step of determining the alpha value for the pixel as one plus the value of a red component of the pixel from the foreground image layer scene rendered over black minus the value of the red component of the corresponding pixel from the foreground image layer scene rendered over white.

7. The method of claim 4 comprising additionally the steps of providing a third image layer and compositing the background image layer, the foreground image layer, and the third image layer to form a multi-layer image with the third image layer appearing between the background image layer and the foreground image layer in the composited multi-layer image.

8. The method of claim 4 wherein the step of rendering a background image layer includes the step of rendering an RGB background image layer.