raster

Documentation

Overview

Package raster is the shared pixel-buffer substrate of go-gfx: a densely packed 8-bit RGBA image the higher layers (resample, color, and the fleet's image-processing and rendering libraries) read and write.

Image.Pix is row-major, four bytes (R, G, B, A) per pixel, with NO row padding — stride is always 4*W. The bytes are STRAIGHT (non-premultiplied): a pixel's colour is stored as-is, independent of its alpha, which is the representation image processing wants. This differs from the standard library's image.RGBA, whose bytes are premultiplied; FromImage and ToRGBA convert across that boundary correctly rather than copying bytes blindly.

Index

• type Image
  • func FromImage(src image.Image) *Image
  • func New(w, h int) *Image
  • func (p *Image) At(x, y int) color.RGBA
  • func (p *Image) Bounds() image.Rectangle
  • func (p *Image) PixOffset(x, y int) int
  • func (p *Image) Set(x, y int, c color.RGBA)
  • func (p *Image) ToNRGBA() *image.NRGBA

Types

type Image

type Image struct {
	Pix  []uint8
	W, H int
}

Image is a densely packed, straight-alpha 8-bit RGBA pixel buffer of W by H pixels. Pix has length 4*W*H.

func FromImage

func FromImage(src image.Image) *Image

FromImage converts any image.Image into a straight-alpha Image. An *image.NRGBA (already straight) is copied directly; anything else is converted pixel by pixel through the non-premultiplied colour model, so a premultiplied *image.RGBA source is un-premultiplied rather than mis-read.

func New

func New(w, h int) *Image

New returns a zeroed Image of w by h pixels (fully transparent black). w and h must be non-negative.

func (*Image) At

func (p *Image) At(x, y int) color.RGBA

At returns the straight-alpha colour of the pixel at (x, y).

func (*Image) Bounds

func (p *Image) Bounds() image.Rectangle

Bounds returns the image's rectangle, anchored at the origin.

func (*Image) PixOffset

func (p *Image) PixOffset(x, y int) int

PixOffset returns the index into Pix of the pixel at (x, y).

func (*Image) Set

func (p *Image) Set(x, y int, c color.RGBA)

Set writes the straight-alpha colour c to the pixel at (x, y).

func (*Image) ToNRGBA

func (p *Image) ToNRGBA() *image.NRGBA

ToNRGBA returns the buffer as a standard-library *image.NRGBA, whose bytes are also straight, so this is a direct copy and the round trip through the standard image package is lossless.