QColorfromRgb

QColorfromRgb refers to the static function used in the Qt framework to create a QColor from individual red, green, and blue components. Implemented as QColor::fromRgb, it provides a programmatic way to specify a color by its 8-bit channel values rather than by a named color or a prebuilt palette.

The function takes three integers, r, g, and b, each in the range 0 to 255, representing the intensities of the red, green, and blue channels. An optional alpha component may be provided to indicate opacity, with 255 meaning fully opaque and 0 representing full transparency. If any input value falls outside the 0–255 range, it is clamped to the nearest valid value. The call returns a QColor object that encodes the specified RGB color, optionally with the chosen alpha.

QColor::fromRgb is commonly used when colors are computed at runtime, loaded from external data, or defined by user input. It is functionally equivalent to constructing a QColor directly with the r, g, and b values, but can be clearer in intent when colors are produced from numeric channels rather than literals. The function also complements other constructors and helpers, such as QColor(r, g, b) and color-per-channel utilities like fromRgbF, which accepts normalized float values.

In practice, developers use QColor::fromRgb to set colors for widgets, painters, palettes, and stylesheets without relying on named colors. This approach emphasizes exact color control and can simplify dynamic theming and color manipulation in Qt applications.