Package draw
import "exp/draw"
Package draw provides basic graphics and drawing primitives, in the style of the Plan 9 graphics library (see http://plan9.bell-labs.com/magic/man2html/2/draw) and the X Render extension.
Package files
arith.go color.go draw.go event.gofunc Border
func Border(dst Image, r Rectangle, w int, src image.Image, sp Point)
Border aligns r.Min in dst with sp in src and then replaces pixels in a w-pixel border around r in dst with the result of the Porter-Duff compositing operation “src over dst.” If w is positive, the border extends w pixels inside r. If w is negative, the border extends w pixels outside r.
func Draw
func Draw(dst Image, r Rectangle, src image.Image, sp Point)
Draw calls DrawMask with a nil mask and an Over op.
func DrawMask
func DrawMask(dst Image, r Rectangle, src image.Image, sp Point, mask image.Image, mp Point, op Op)
DrawMask aligns r.Min in dst with sp in src and mp in mask and then replaces the rectangle r in dst with the result of a Porter-Duff composition. A nil mask is treated as opaque. The implementation is simple and slow. TODO(nigeltao): Optimize this.
type Color
A Color represents a color with 8-bit R, G, B, and A values, packed into a uint32—0xRRGGBBAA—so that comparison is defined on colors. Color implements image.Color. Color also implements image.Image: it is a 10⁹x10⁹-pixel image of uniform color.
type Color uint32
var (
Opaque Color = 0xFFFFFFFF
Transparent Color = 0x00000000
Black Color = 0x000000FF
White Color = 0xFFFFFFFF
Red Color = 0xFF0000FF
Green Color = 0x00FF00FF
Blue Color = 0x0000FFFF
Cyan Color = 0x00FFFFFF
Magenta Color = 0xFF00FFFF
Yellow Color = 0xFFFF00FF
PaleYellow Color = 0xFFFFAAFF
DarkYellow Color = 0xEEEE9EFF
DarkGreen Color = 0x448844FF
PaleGreen Color = 0xAAFFAAFF
MedGreen Color = 0x88CC88FF
DarkBlue Color = 0x000055FF
PaleBlueGreen Color = 0xAAFFFFFF
PaleBlue Color = 0x0000BBFF
BlueGreen Color = 0x008888FF
GreyGreen Color = 0x55AAAAFF
PaleGreyGreen Color = 0x9EEEEEFF
YellowGreen Color = 0x99994CFF
MedBlue Color = 0x000099FF
GreyBlue Color = 0x005DBBFF
PaleGreyBlue Color = 0x4993DDFF
PurpleBlue Color = 0x8888CCFF
)
func (Color) At
func (c Color) At(x, y int) image.Color
func (Color) ColorModel
func (c Color) ColorModel() image.ColorModel
func (Color) Height
func (c Color) Height() int
func (Color) RGBA
func (c Color) RGBA() (r, g, b, a uint32)
func (Color) SetAlpha
func (c Color) SetAlpha(a uint8) Color
SetAlpha returns the color obtained by changing c's alpha value to a and scaling r, g, and b appropriately.
func (Color) Width
func (c Color) Width() int
type Context
A Context represents a single graphics window.
type Context interface {
// Screen returns an editable Image of window.
Screen() Image
// FlushImage flushes changes made to Screen() back to screen.
FlushImage()
// KeyboardChan returns a channel carrying keystrokes.
// An event is sent each time a key is pressed or released.
// The value k represents key k being pressed.
// The value -k represents key k being released.
// The specific set of key values is not specified,
// but ordinary character represent themselves.
KeyboardChan() <-chan int
// MouseChan returns a channel carrying mouse events.
// A new event is sent each time the mouse moves or a
// button is pressed or released.
MouseChan() <-chan Mouse
// ResizeChan returns a channel carrying resize events.
// An event is sent each time the window is resized;
// the client should respond by calling Screen() to obtain
// the new screen image.
// The value sent on the channel is always ``true'' and can be ignored.
ResizeChan() <-chan bool
// QuitChan returns a channel carrying quit requests.
// After reading a value from the quit channel, the application
// should exit.
QuitChan() <-chan bool
}
type Image
A draw.Image is an image.Image with a Set method to change a single pixel.
type Image interface {
image.Image
Set(x, y int, c image.Color)
}
type Mouse
A Mouse represents the state of the mouse.
type Mouse struct {
Buttons int // bit mask of buttons: 1<<0 is left, 1<<1 middle, 1<<2 right
Point // location of cursor
Nsec int64 // time stamp
}
type Op
A Porter-Duff compositing operator.
type Op int
const (
// Over specifies ``(src in mask) over dst''.
Over Op = iota
// Src specifies ``src in mask''.
Src
)
type Point
A Point is an X, Y coordinate pair.
type Point struct {
X, Y int
}
ZP is the zero Point.
var ZP Point
func Pt
func Pt(X, Y int) Point
Pt is shorthand for Point{X, Y}.
func (Point) Add
func (p Point) Add(q Point) Point
Add returns the sum of p and q: Pt(p.X+q.X, p.Y+q.Y).
func (Point) Div
func (p Point) Div(k int) Point
Div returns p divided by k: Pt(p.X/k, p.Y/k).
func (Point) Eq
func (p Point) Eq(q Point) bool
Eq returns true if p and q are equal.
func (Point) Mul
func (p Point) Mul(k int) Point
Mul returns p scaled by k: Pt(p.X*k p.Y*k).
func (Point) Sub
func (p Point) Sub(q Point) Point
Sub returns the difference of p and q: Pt(p.X-q.X, p.Y-q.Y).
type Rectangle
A Rectangle contains the Points with Min.X <= X < Max.X, Min.Y <= Y < Max.Y.
type Rectangle struct {
Min, Max Point
}
ZR is the zero Rectangle.
var ZR Rectangle
func Rect
func Rect(x0, y0, x1, y1 int) Rectangle
Rect is shorthand for Rectangle{Pt(x0, y0), Pt(x1, y1)}.
func Rpt
func Rpt(min, max Point) Rectangle
Rpt is shorthand for Rectangle{min, max}.
func (Rectangle) Add
func (r Rectangle) Add(p Point) Rectangle
Add returns the rectangle r translated by p: Rpt(r.Min.Add(p), r.Max.Add(p)).
func (Rectangle) Canon
func (r Rectangle) Canon() Rectangle
Canon returns a canonical version of r: the returned rectangle has Min.X <= Max.X and Min.Y <= Max.Y.
func (Rectangle) Clip
func (r Rectangle) Clip(r1 Rectangle) Rectangle
Clip returns the largest rectangle containing only points shared by r and r1.
func (Rectangle) Combine
func (r Rectangle) Combine(r1 Rectangle) Rectangle
Combine returns the smallest rectangle containing all points from r and from r1.
func (Rectangle) Dx
func (r Rectangle) Dx() int
Dx returns the width of the rectangle r: r.Max.X - r.Min.X.
func (Rectangle) Dy
func (r Rectangle) Dy() int
Dy returns the width of the rectangle r: r.Max.Y - r.Min.Y.
func (Rectangle) Empty
func (r Rectangle) Empty() bool
Empty retruns true if r contains no points.
func (Rectangle) In
func (r Rectangle) In(r1 Rectangle) bool
InRect returns true if all the points in r are also in r1.
func (Rectangle) Inset
func (r Rectangle) Inset(n int) Rectangle
Inset returns the rectangle r inset by n: Rect(r.Min.X+n, r.Min.Y+n, r.Max.X-n, r.Max.Y-n).
func (Rectangle) Overlaps
func (r Rectangle) Overlaps(r1 Rectangle) bool
Overlaps returns true if r and r1 cross; that is, it returns true if they share any point.
func (Rectangle) Sub
func (r Rectangle) Sub(p Point) Rectangle
Sub returns the rectangle r translated by -p: Rpt(r.Min.Sub(p), r.Max.Sub(p)).
Bugs
This is a toy library and not ready for production use.
Subdirectories
| Name | Synopsis | |
|---|---|---|
| .. | ||
| x11 | This package implements an X11 backend for the exp/draw package. |