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v0 source pure

Package canvas is a fixed-size, 16-color pixel grid.

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canvas

Pure package gno.land/p/g1sw5xklxjjuv0yvuxy5f5s3l3mnj0nqq626a9wr/canvas/v0: a fixed-size grid of palette indexes with lazy per-row allocation, plus the x,y,color;... batch codec.

Used by the realm gno.land/r/g1sw5xklxjjuv0yvuxy5f5s3l3mnj0nqq626a9wr/million/v0, which adds pricing and access control. The package itself holds no chain state and has no chain imports, so it is fully covered by plain unit tests (gno test .).

  • New(width, height): empty canvas, sides between 1 and 10000.
  • Set(Pixel), Get(x, y), Check(Pixel): paint, read, validate.
  • Rows(from, to): rows as one hex digit per pixel, no separators.
  • ParsePixels, Encode, ParseColor: the batch format.
  • Palette: 16 CSS colors, index 0 being "never painted".

Overview

Package canvas is a fixed-size, 16-color pixel grid.

It holds no chain state and knows nothing about payments: the realm gno.land/r/g1sw5xklxjjuv0yvuxy5f5s3l3mnj0nqq626a9wr/million/v0 wraps it with pricing and access control.

Storage layout: one []byte per row, allocated on first paint. A row that was never painted is nil and costs nothing. Each byte holds a palette index; Blank (0) means "never painted".

Constants 1

const Blank, MaxColor, MaxSide 

1const (
2	// Blank is the color of a pixel nobody painted. It cannot be painted.
3	Blank byte = 0
4	// MaxColor is the highest valid palette index.
5	MaxColor byte = 15
6	// MaxSide bounds width and height so x*y fits comfortably in an int.
7	MaxSide = 10000
8)
source

Variables 2

var Palette 

 1var Palette = [MaxColor + 1]string{
 2	"#ffffff",
 3	"#ffffff",
 4	"#e4e4e4",
 5	"#888888",
 6	"#222222",
 7	"#ffa7d1",
 8	"#e50000",
 9	"#e59500",
10	"#a06a42",
11	"#e5d900",
12	"#94e044",
13	"#02be01",
14	"#00d3dd",
15	"#0083c7",
16	"#cf6ee4",
17	"#820080",
18}
source

Palette maps a color index to its CSS hex value. Index 0 is Blank and is rendered as white by clients.

Functions 4

func Encode 

1func Encode(pixels []Pixel) string
source

Encode is the inverse of ParsePixels.

func ParseColor 

1func ParseColor(s string) (byte, error)
source

ParseColor converts a decimal color index, rejecting Blank.

func New 

1func New(width, height int) *Canvas
source

New returns an empty canvas. It panics on a non-positive or oversized side.

func ParsePixels 

1func ParsePixels(s string) ([]Pixel, error)
source

ParsePixels decodes "x,y,color;x,y,color;...". A trailing ';' is allowed. It validates the syntax and the color range but not the coordinates, which depend on the canvas: call Check for that.

Types 2

type Canvas

struct 
1type Canvas struct {
2	width, height int
3	rows          [][]byte
4	painted       int
5}
source

Canvas is a width x height grid of palette indexes.

Methods on Canvas

func Check

method on Canvas 
1func (c *Canvas) Check(p Pixel) error
source

Check reports whether p can be painted on this canvas.

func Get

method on Canvas 
1func (c *Canvas) Get(x, y int) byte
source

Get returns the color at (x, y). Out-of-range coordinates panic.

func Height

method on Canvas 
1func (c *Canvas) Height() int
source

func Painted

method on Canvas 
1func (c *Canvas) Painted() int
source

Painted is the number of pixels that are not Blank.

func Rows

method on Canvas 
1func (c *Canvas) Rows(from, to int) string
source

Rows encodes rows [from, to) as one hex digit per pixel, row after row, with no separator. Clients slice it with the known width.

func Set

method on Canvas 
1func (c *Canvas) Set(p Pixel)
source

Set paints p. It panics when Check(p) fails.

func Width

method on Canvas 
1func (c *Canvas) Width() int
source

type Pixel

struct 
1type Pixel struct {
2	X, Y  int
3	Color byte
4}
source

Pixel is one paint request.

Imports 3

  • errors stdlib
  • strconv stdlib
  • strings stdlib

Source Files 4