1// Copyright 2015 The Go Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style 3// license that can be found in the LICENSE file. 4 5// Package draw provides image composition functions. 6// 7// See "The Go image/draw package" for an introduction to this package: 8// http://golang.org/doc/articles/image_draw.html 9// 10// This package is a superset of and a drop-in replacement for the image/draw 11// package in the standard library. 12package draw 13 14// This file just contains the API exported by the image/draw package in the 15// standard library. Other files in this package provide additional features. 16 17import ( 18 "image" 19 "image/color" 20 "image/draw" 21) 22 23// Draw calls DrawMask with a nil mask. 24func Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point, op Op) { 25 draw.Draw(dst, r, src, sp, draw.Op(op)) 26} 27 28// DrawMask aligns r.Min in dst with sp in src and mp in mask and then 29// replaces the rectangle r in dst with the result of a Porter-Duff 30// composition. A nil mask is treated as opaque. 31func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mask image.Image, mp image.Point, op Op) { 32 draw.DrawMask(dst, r, src, sp, mask, mp, draw.Op(op)) 33} 34 35// Drawer contains the Draw method. 36type Drawer interface { 37 // Draw aligns r.Min in dst with sp in src and then replaces the 38 // rectangle r in dst with the result of drawing src on dst. 39 Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point) 40} 41 42// FloydSteinberg is a Drawer that is the Src Op with Floyd-Steinberg error 43// diffusion. 44var FloydSteinberg Drawer = floydSteinberg{} 45 46type floydSteinberg struct{} 47 48func (floydSteinberg) Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point) { 49 draw.FloydSteinberg.Draw(dst, r, src, sp) 50} 51 52// Image is an image.Image with a Set method to change a single pixel. 53type Image interface { 54 image.Image 55 Set(x, y int, c color.Color) 56} 57 58// Op is a Porter-Duff compositing operator. 59type Op int 60 61const ( 62 // Over specifies ``(src in mask) over dst''. 63 Over Op = Op(draw.Over) 64 // Src specifies ``src in mask''. 65 Src Op = Op(draw.Src) 66) 67 68// Draw implements the Drawer interface by calling the Draw function with 69// this Op. 70func (op Op) Draw(dst Image, r image.Rectangle, src image.Image, sp image.Point) { 71 (draw.Op(op)).Draw(dst, r, src, sp) 72} 73 74// Quantizer produces a palette for an image. 75type Quantizer interface { 76 // Quantize appends up to cap(p) - len(p) colors to p and returns the 77 // updated palette suitable for converting m to a paletted image. 78 Quantize(p color.Palette, m image.Image) color.Palette 79} 80