Pixel Formats topic

A PixelFormat is a description of how pixel data is stored in memory. It includes a set of standard properties and rules for how to interpret the data, such as how many bytes are used to store each pixel, canonical (zero or max) values, and conversion rules to and from other formats.

Pxl ships with a number of built-in pixel formats, and can be extended with additional formats:

const myFormat = const MyFormat._();

//                         Pixel data type    Channel data type
//                                       v    v
final class MyFormat extends PixelFormat<int, int> {
  const MyFormat._();

  @override
  int get bytesPerPixel => 4;

  @override
  int get zero => 0;

  // ... rest of the class implementation
}

Integer pixel formats

All integer formats use the ABGR 32-bit format as a common intermediate for conversions; channels that are larger or smaller than 8 bits are scaled to fit within the 8-bit range. For example a 4-bit channel value of 0x0F would be scaled to 0xFF when converting to 8-bit.

Grayscale formats use luminance values to represent color.

Floating-point pixel formats

All floating-point formats use the RGBA 128-bit format as a common intermediate for conversions; channels that are larger or smaller than 32 bits are scaled to fit within the 32-bit range. When converting to packed integer formats, data is normalized to the range [0.0, 1.0] and then scaled to fit within the integer range.

Indexed pixel formats

IndexedFormats use a palette to map pixel values to colors.

The palette is stored as a separate array of colors, and the pixel data is stored as indices into the palette.

// Example of a 1-bit indexed format.
final mono1 = IndexedPixelFormat.bits8(
  const [0xFF000000, 0xFFFFFFFF],
  format: abgr8888,
);