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| 1 // Copyright 2014 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. |
| 12 package 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 |
| 17 import ( |
| 18 "image" |
| 19 "image/color" |
| 20 "image/draw" |
| 21 ) |
| 22 |
| 23 // Draw calls DrawMask with a nil mask. |
| 24 func 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. |
| 31 func DrawMask(dst Image, r image.Rectangle, src image.Image, sp image.Point, mas
k 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. |
| 36 type 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. |
| 44 var FloydSteinberg Drawer = floydSteinberg{} |
| 45 |
| 46 type floydSteinberg struct{} |
| 47 |
| 48 func (floydSteinberg) Draw(dst Image, r image.Rectangle, src image.Image, sp ima
ge.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. |
| 53 type Image interface { |
| 54 image.Image |
| 55 Set(x, y int, c color.Color) |
| 56 } |
| 57 |
| 58 // Op is a Porter-Duff compositing operator. |
| 59 type Op int |
| 60 |
| 61 const ( |
| 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. |
| 70 func (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. |
| 75 type 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 } |
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