Per-Pixel Alpha-Blending for Smooth Window Corners

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Solution Overview

Problem

Existing alpha-blending techniques struggle to seamlessly integrate transparent windows with desktops and other windows, particularly in achieving smooth anti-aliasing of window corners against backgrounds, due to limitations in interacting with the desktop or other windows.

Innovation Solution

A method and system for alpha-blending a window with a background image, involving a window manager, an alpha-blender, and a rendering agent that captures and blends window and background images, allowing for partial transparency and smooth edge rendering by determining alpha channel values and generating a composite image for display.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional alpha-blending techniques are used to blend two images, then the blending process is simple, but it cannot integrate windows with desktops or other windows and cannot achieve smooth anti-aliasing of window corners

Engineering Contradiction:

Improveability to blend window with backgroundVSAvoidcomplexity of alpha-blending system

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent introduces a background image as an intermediary element between the window and the display. Instead of directly blending the window with the desktop or other windows, the system captures a background image (which may include desktop elements or other windows) and uses this as the base layer for alpha-blending the window, thereby achieving smooth integration and anti-aliasing

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system performs preliminary capture of the background image before applying the window overlay. By capturing the background state first (using coordinates to define the region), the system prepares the base layer that will be blended with the window, enabling smooth anti-aliasing effects at the window boundaries

Inventive Principle:

Principle #10Preliminary action

2Shape

If transparent window borders are used, then the window appearance is modern and clean, but it interferes with alpha-blending and prevents smooth corner rendering

Engineering Contradiction:

Improvesmoothness of window cornersVSAvoiddifficulty of achieving alpha-blending

Core Design Contradiction:

ShapeVSEase of manufacture

Solution Approach 1:

The patent applies local quality by capturing and blending only the specific background region where the window is located, rather than handling the entire desktop. By focusing the alpha-blending operation on the local background area defined by window coordinates, the system achieves smooth corner rendering without needing to manage transparent borders across the entire display

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system changes the parameter of background representation from a static desktop environment to a captured image with defined coordinates. By obtaining background image coordinates that match the window position, the system enables precise local blending that produces smooth anti-aliased corners while avoiding the complications of transparent window borders

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8723887B2Methods and systems for per pixel alpha-blending of a parent window and a portion of a background image

Publication Date: 2014.05.13 CITRIX SYSTEMS INC

AI summary

A system for alpha blending at least a portion of an image of a window with a background image, where the image of the window is captured by an alpha blender and blended together with an image of the background also captured by the alpha blender. The resulting alpha-blended image is then displayed within the window to give at least a portion of the window the appearance of smooth, anti-aliased edges.