from_known_color()

static xtd::drawing::color xtd::drawing::color::from_known_color ( xtd::drawing::known_color  color )

static

Creates a xtd::drawing::color class from the four ARGB component (alpha, red, green, and blue) values. Although this method allows a 32-bit value to be passed for each component, the value of each component is limited to 8 bits.

Parameters

alpha	The alpha value for the new xtd::drawing::color. Valid values are 0 through 255.
red	The red component. Valid values are 0 through 255.
green	The green component. Valid values are 0 through 255.
blue	The blue component. Valid values are 0 through 255.

Returns

xtd::drawing::color The xtd::drawing::color structure that this method creates.

Exceptions

std::invalid_argument

color is not a known_color.

Examples

The following code example is designed for use with Windows Forms, and it requires xtd::forms::paint_event_args, which is a parameter of the xtd::forms::control::paint event handler. The code performs the following actions:

• Creates an instance of a xtd::drawing::color structure, redShade, to be used for comparisons.
• Iterates through the xtd::drawing::known_color enumeration elements to find all known colors that have the same lightness as redShade. The iterations are terminated when 15 matches are found or the value of the loop counter is greater than the last xtd::drawing::known_color element.
• During each iteration, saves the xtd::drawing::known_color element—if it matches the criteria—in an array.
• Uses a brush to paint rectangles. The first rectangle is painted the color represented by redShade. Each of the other rectangles is painted a xtd::drawing::known_color that matches the hue of the redShade.

  void known_color_brightness_example2(paint_event_args& e) {
    graphics g = e.graphics();
   
    // xtd::drawing::color structures. One is a variable used for temporary storage. The other is a constant used for comparisons.
    xtd::drawing::color some_color = xtd::drawing::color::from_argb(0);
    xtd::drawing::color red_shade = xtd::drawing::color::from_argb(255, 200, 0, 100);
   
    // Array to store xtd::drawing::known_color values that match the hue of the redShade color.
    std::vector<xtd::drawing::known_color> color_matches(15);
   
    // Number of matches found.
    int count = 0;
   
    // Iterate through the xtd::drawing::known_color enums until 15 matches are found.
    for (xtd::drawing::known_color enum_value = 0; enum_value <= xtd::drawing::known_color::yellow_green && count < 15; enum_value = known_color(int(enum_value) + 1)) {
      some_color = xtd::drawing::color::from_known_color(enum_value);
      if (some_color.get_brightness() == red_shade.get_brightness())
        color_matches[count++] = enum_value;
    }
   
    // Display the redShade color and its argb value.
    solid_brush  my_brush1(red_shade);
    font my_font("Arial", 12);
    int x = 20;
    int y = 20;
    some_color = red_shade;
    g.fill_rectangle(my_brush1, x, y, 100, 30);
    g.draw_string(some_color.to_string(), my_font, brushes::black, x + 120, y);
   
    // Iterate through the matches that were found and display each color that corresponds with the enum value in the array. also display the name of the xtd::drawing::known_color.
    for (int i = 0; i < count; i++) {
      y += 40;
      some_color = xtd::drawing::color::from_known_color(color_matches[i]);
      my_brush1.xtd::drawing::color = some_color;
      g.fill_rectangle(my_brush1, x, y, 100, 30);
      g.draw_string(some_color.to_string(), my_font, brushes::black, x + 120, y);
    }
  }