Represents a color in the RGBA color space. This representation is designed for simplicity of conversion to/from color representations in various languages over compactness; for example, the fields of this representation can be trivially provided to the constructor of "java.awt.Color" in Java; it can also be trivially provided to UIColor's "+colorWithRed:green:blue:alpha" method in iOS; and, with just a little work, it can be easily formatted into a CSS "rgba()" string in JavaScript, as well.

Note: this proto does not carry information about the absolute color space that should be used to interpret the RGB value (e.g. sRGB, Adobe RGB, DCI-P3, BT.2020, etc.). By default, applications SHOULD assume the sRGB color space.

Example (Java):


 // ...
 public static java.awt.Color fromProto(Color protocolor) {
   float alpha = protocolor.hasAlpha()
       ? protocolor.getAlpha().getValue()
       : 1.0;

   return new java.awt.Color(

 public static Color toProto(java.awt.Color color) {
   float red = (float) color.getRed();
   float green = (float) color.getGreen();
   float blue = (float) color.getBlue();
   float denominator = 255.0;
   Color.Builder resultBuilder =
           .setRed(red / denominator)
           .setGreen(green / denominator)
           .setBlue(blue / denominator);
   int alpha = color.getAlpha();
   if (alpha != 255) {
             .setValue(((float) alpha) / denominator)
 // ...

Example (iOS / Obj-C):

 // ...
 static UIColor* fromProto(Color* protocolor) {
    float red = [protocolor red];
    float green = [protocolor green];
    float blue = [protocolor blue];
    FloatValue* alpha_wrapper = [protocolor alpha];
    float alpha = 1.0;
    if (alpha_wrapper != nil) {
      alpha = [alpha_wrapper value];
    return [UIColor colorWithRed:red green:green blue:blue alpha:alpha];

 static Color* toProto(UIColor* color) {
     CGFloat red, green, blue, alpha;
     if (![color getRed:&red green:&green blue:&blue alpha:&alpha]) {
       return nil;
     Color* result = [[Color alloc] init];
     [result setRed:red];
     [result setGreen:green];
     [result setBlue:blue];
     if (alpha <= 0.9999) {
       [result setAlpha:floatWrapperWithValue(alpha)];
     [result autorelease];
     return result;
// ...

Example (JavaScript):

// ...

var protoToCssColor = function(rgb_color) {
   var redFrac = || 0.0;
   var greenFrac = || 0.0;
   var blueFrac = || 0.0;
   var red = Math.floor(redFrac * 255);
   var green = Math.floor(greenFrac * 255);
   var blue = Math.floor(blueFrac * 255);

   if (!('alpha' in rgb_color)) {
      return rgbToCssColor_(red, green, blue);

   var alphaFrac = rgb_color.alpha.value || 0.0;
   var rgbParams = [red, green, blue].join(',');
   return ['rgba(', rgbParams, ',', alphaFrac, ')'].join('');

var rgbToCssColor_ = function(red, green, blue) {
  var rgbNumber = new Number((red << 16) | (green << 8) | blue);
  var hexString = rgbNumber.toString(16);
  var missingZeros = 6 - hexString.length;
  var resultBuilder = ['#'];
  for (var i = 0; i < missingZeros; i++) {
  return resultBuilder.join('');

// ...
JSON representation
  "red": number,
  "green": number,
  "blue": number,
  "alpha": number


The amount of red in the color as a value in the interval [0, 1].



The amount of green in the color as a value in the interval [0, 1].



The amount of blue in the color as a value in the interval [0, 1].



The fraction of this color that should be applied to the pixel. That is, the final pixel color is defined by the equation:

pixel color = alpha * (this color) + (1.0 - alpha) * (background color)

This means that a value of 1.0 corresponds to a solid color, whereas a value of 0.0 corresponds to a completely transparent color. This uses a wrapper message rather than a simple float scalar so that it is possible to distinguish between a default value and the value being unset. If omitted, this color object is to be rendered as a solid color (as if the alpha value had been explicitly given with a value of 1.0).

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