Linear gradient initialization and control functions

This part of the API performs linear gradient operations.

A color gradient (color progression, color ramp) is a smooth transition between a set of colors (color stops) that is done along a line (linear, or axial color gradient) or radially, along concentric circles (radial color gradient). The color transition is done by linear interpolation between two consecutive color stops.

Note: VGLite supports linear color gradients for GCNanoLiteV and GCNanoUltraV. Both linear and radial gradients are supported with GC355 and GC555.

vg_lite_init_grad function

Description:

This function initializes the internal buffer for the linear gradient object with default settings for rendering.

Syntax:

vg_lite_error_t vg_lite_init_grad (
       vg_lite_linear_gradient_t *grad
);

Parameters:

Parameter	Description
*grad	Pointer to the vg_lite_linear_gradient_t structure, which defines the gradient to be initialized. Default values are used.

Returns:

Returns VG_LITE_SUCCESS if successful. See vg_lite_error_t enum for other return codes.

Parent topic:Linear gradient initialization and control functions

vg_lite_clear_grad function

Description:

This function is used to clear the values of a linear gradient object and free up the memory of the image buffer.

Syntax:

vg_lite_error_t vg_lite_clear_grad (
       vg_lite_linear_gradient_t        *grad
);

Parameters:

Parameter	Description
*grad	Pointer to the vg_lite_linear_gradient_t structure that is to be cleared

Returns:

Returns VG_LITE_SUCCESS if successful. See vg_lite_error_t enum for other return codes.

Parent topic:Linear gradient initialization and control functions

vg_lite_set_grad function

Description:

This function is used to set values for the members of the vg_lite_linear_gradient_t structure.

Note: The vg_lite_set_grad API adopts the following rules to set the default gradient colors if the input parameters are incomplete or invalid:

• If no valid stops have been specified (for example, due to an empty input array, out-of-range or out-of-order stops), a stop at 0 with (R, G, B, A) color (0.0, 0.0, 0.0, 1.0) (opaque black) and a stop at 1 with color (1.0, 1.0, 1.0, 1.0) (opaque white) are implicitly defined

• If at least one valid stop has been specified, but none has been defined with an offset of 0, then an implicit stop is added with an offset of 0 and the same color as the first user-defined stop

• If at least one valid stop has been specified, but none has been defined with an offset of 1, then an implicit stop is added with an offset of 1 and the same color as the last user-defined stop

Syntax:

vg_lite_error_t vg_lite_set_grad (
       vg_lite_linear_gradient_t       *grad,
       uint32_t                        count,
       uint32_t                        *colors,
       uint32_t                        *stops
      );

Parameters:

Parameter	Description
*grad	Pointer to the vg_lite_linear_gradient_t structure to be set
count	The number of colors in the linear gradient. The maximum color stop count is defined by VLC_MAX_GRAD which is 16.
*colors	Specifies the color array for the gradient stops. The color is in ARGB8888 format with alpha in the upper byte.
*stops	Pointer to the gradient stop offset

Returns:

Always returns VG_LITE_SUCCESS.

Parent topic:Linear gradient initialization and control functions

vg_lite_get_grad_matrix function

Description:

This function is used to get a pointer to the transformation matrix of the gradient object. It allows an application to manipulate the matrix to facilitate correct rendering of the gradient path.

Syntax:

vg_lite_error_t vg_lite_get_grad_matrix (
       vg_lite_linear_gradient_t         *grad
);

Parameters:

Parameter	Description
*grad	Pointer to the vg_lite_linear_gradient_t structure, which contains the matrix to be retrieved

Returns:

Returns VG_LITE_SUCCESS if successful. See vg_lite_error_t enum for other return codes.

Parent topic:Linear gradient initialization and control functions

vg_lite_update_grad function

Description:

This function is used to update or generate values for an image object that is going to be rendered. The vg_lite_linear_gradient_t object has an image buffer, which is used to render the gradient pattern. The image buffer is created or updated with the corresponding gradient parameters.

Syntax:

vg_lite_error_t vg_lite_update_grad (
       vg_lite_linear_gradient_t     *grad
);

Parameters:

Parameter	Description
*grad	Pointer to the vg_lite_linear_gradient_t structure, which contains the update values to be used for the object to be rendered

Returns:

Returns VG_LITE_SUCCESS if successful. See vg_lite_error_t enum for other return codes.

Parent topic:Linear gradient initialization and control functions

Parent topic:Vector-dased draw operations