Put the RGBA values that correspond to color_string in rgba_color.
@param color_string a string specifying a color. It can be the name of
a color (case insensitive match) or a [0x|#]RRGGBBAA sequence,
possibly followed by "@" and a string representing the alpha
component.
The alpha component may be a string composed by "0x" followed by an
hexadecimal number or a decimal number between 0.0 and 1.0, which
represents the opacity value (0x00/0.0 means completely transparent,
0xff/1.0 completely opaque).
If the alpha component is not specified then 0xff is assumed.
The string "random" will result in a random color.
@param slen length of the initial part of color_string containing the
color. It can be set to -1 if color_string is a null terminated string
containing nothing else than the color.
@return >= 0 in case of success, a negative value in case of
failure (for example if color_string cannot be parsed).
Put the RGBA values that correspond to color_string in rgba_color.
@param color_string a string specifying a color. It can be the name of a color (case insensitive match) or a [0x|#]RRGGBBAA sequence, possibly followed by "@" and a string representing the alpha component. The alpha component may be a string composed by "0x" followed by an hexadecimal number or a decimal number between 0.0 and 1.0, which represents the opacity value (0x00/0.0 means completely transparent, 0xff/1.0 completely opaque). If the alpha component is not specified then 0xff is assumed. The string "random" will result in a random color. @param slen length of the initial part of color_string containing the color. It can be set to -1 if color_string is a null terminated string containing nothing else than the color. @return >= 0 in case of success, a negative value in case of failure (for example if color_string cannot be parsed).