image/color: simplify documentation

R=nigeltao, dsymonds, adg
CC=golang-dev
https://golang.org/cl/5544073

diff --git a/src/pkg/image/color/color.go b/src/pkg/image/color/color.go
index 2948db7f38cc49ac61a1aa989caf082bdac03328..29a7b8a40011408864ed3e12ddb779b7bbbca135 100644 (file)
--- a/src/pkg/image/color/color.go
+++ b/src/pkg/image/color/color.go
@@ -152,26 +152,35 @@ func (m *modelFunc) Convert(c Color) Color {
        return m.f(c)
 }
 
-// RGBAModel is the Model for RGBA colors.
-var RGBAModel Model = ModelFunc(func(c Color) Color {
+// Models for the standard color types.
+var (
+       RGBAModel    Model = ModelFunc(rgbaModel)
+       RGBA64Model  Model = ModelFunc(rgba64Model)
+       NRGBAModel   Model = ModelFunc(nrgbaModel)
+       NRGBA64Model Model = ModelFunc(nrgba64Model)
+       AlphaModel   Model = ModelFunc(alphaModel)
+       Alpha16Model Model = ModelFunc(alpha16Model)
+       GrayModel    Model = ModelFunc(grayModel)
+       Gray16Model  Model = ModelFunc(gray16Model)
+)
+
+func rgbaModel(c Color) Color {
        if _, ok := c.(RGBA); ok {
                return c
        }
        r, g, b, a := c.RGBA()
        return RGBA{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
-})
+}
 
-// RGBAModel is the Model for RGBA64 colors.
-var RGBA64Model Model = ModelFunc(func(c Color) Color {
+func rgba64Model(c Color) Color {
        if _, ok := c.(RGBA64); ok {
                return c
        }
        r, g, b, a := c.RGBA()
        return RGBA64{uint16(r), uint16(g), uint16(b), uint16(a)}
-})
+}
 
-// NRGBAModel is the Model for NRGBA colors.
-var NRGBAModel Model = ModelFunc(func(c Color) Color {
+func nrgbaModel(c Color) Color {
        if _, ok := c.(NRGBA); ok {
                return c
        }
@@ -187,10 +196,9 @@ var NRGBAModel Model = ModelFunc(func(c Color) Color {
        g = (g * 0xffff) / a
        b = (b * 0xffff) / a
        return NRGBA{uint8(r >> 8), uint8(g >> 8), uint8(b >> 8), uint8(a >> 8)}
-})
+}
 
-// NRGBAModel is the Model for NRGBA64 colors.
-var NRGBA64Model Model = ModelFunc(func(c Color) Color {
+func nrgba64Model(c Color) Color {
        if _, ok := c.(NRGBA64); ok {
                return c
        }
@@ -206,45 +214,41 @@ var NRGBA64Model Model = ModelFunc(func(c Color) Color {
        g = (g * 0xffff) / a
        b = (b * 0xffff) / a
        return NRGBA64{uint16(r), uint16(g), uint16(b), uint16(a)}
-})
+}
 
-// AlphaModel is the Model for Alpha colors.
-var AlphaModel Model = ModelFunc(func(c Color) Color {
+func alphaModel(c Color) Color {
        if _, ok := c.(Alpha); ok {
                return c
        }
        _, _, _, a := c.RGBA()
        return Alpha{uint8(a >> 8)}
-})
+}
 
-// Alpha16Model is the Model for Alpha16 colors.
-var Alpha16Model Model = ModelFunc(func(c Color) Color {
+func alpha16Model(c Color) Color {
        if _, ok := c.(Alpha16); ok {
                return c
        }
        _, _, _, a := c.RGBA()
        return Alpha16{uint16(a)}
-})
+}
 
-// GrayModel is the Model for Gray colors.
-var GrayModel Model = ModelFunc(func(c Color) Color {
+func grayModel(c Color) Color {
        if _, ok := c.(Gray); ok {
                return c
        }
        r, g, b, _ := c.RGBA()
        y := (299*r + 587*g + 114*b + 500) / 1000
        return Gray{uint8(y >> 8)}
-})
+}
 
-// Gray16Model is the Model for Gray16 colors.
-var Gray16Model Model = ModelFunc(func(c Color) Color {
+func gray16Model(c Color) Color {
        if _, ok := c.(Gray16); ok {
                return c
        }
        r, g, b, _ := c.RGBA()
        y := (299*r + 587*g + 114*b + 500) / 1000
        return Gray16{uint16(y)}
-})
+}
 
 // Palette is a palette of colors.
 type Palette []Color
@@ -290,13 +294,10 @@ func (p Palette) Index(c Color) int {
        return ret
 }
 
+// Standard colors.
 var (
-       // Black is an opaque black Color.
-       Black = Gray16{0}
-       // White is an opaque white Color.
-       White = Gray16{0xffff}
-       // Transparent is a fully transparent Color.
+       Black       = Gray16{0}
+       White       = Gray16{0xffff}
        Transparent = Alpha16{0}
-       // Opaque is a fully opaque Color.
-       Opaque = Alpha16{0xffff}
+       Opaque      = Alpha16{0xffff}
 )

diff --git a/src/pkg/image/color/ycbcr.go b/src/pkg/image/color/ycbcr.go
index c79816dd45aa7631e8ebbaeef650a915ff85563c..c6b9ba08db3726a683ac3bf5a0ae4be8a6210596 100644 (file)
--- a/src/pkg/image/color/ycbcr.go
+++ b/src/pkg/image/color/ycbcr.go
@@ -4,8 +4,7 @@
 
 package color
 
-// RGBToYCbCr converts an RGB triple to a Y'CbCr triple. All components lie
-// within the range [0, 255].
+// RGBToYCbCr converts an RGB triple to a Y'CbCr triple.
 func RGBToYCbCr(r, g, b uint8) (uint8, uint8, uint8) {
        // The JFIF specification says:
        //      Y' =  0.2990*R + 0.5870*G + 0.1140*B
@@ -36,8 +35,7 @@ func RGBToYCbCr(r, g, b uint8) (uint8, uint8, uint8) {
        return uint8(yy), uint8(cb), uint8(cr)
 }
 
-// YCbCrToRGB converts a Y'CbCr triple to an RGB triple. All components lie
-// within the range [0, 255].
+// YCbCrToRGB converts a Y'CbCr triple to an RGB triple.
 func YCbCrToRGB(y, cb, cr uint8) (uint8, uint8, uint8) {
        // The JFIF specification says:
        //      R = Y' + 1.40200*(Cr-128)
@@ -89,11 +87,13 @@ func (c YCbCr) RGBA() (uint32, uint32, uint32, uint32) {
 }
 
 // YCbCrModel is the Model for Y'CbCr colors.
-var YCbCrModel Model = ModelFunc(func(c Color) Color {
+var YCbCrModel Model = ModelFunc(modelYCbCr)
+
+func modelYCbCr(c Color) Color {
        if _, ok := c.(YCbCr); ok {
                return c
        }
        r, g, b, _ := c.RGBA()
        y, u, v := RGBToYCbCr(uint8(r>>8), uint8(g>>8), uint8(b>>8))
        return YCbCr{y, u, v}
-})
+}