diff options
Diffstat (limited to 'vendor/github.com/lucasb-eyer')
| -rw-r--r-- | vendor/github.com/lucasb-eyer/go-colorful/README.md | 33 | ||||
| -rw-r--r-- | vendor/github.com/lucasb-eyer/go-colorful/colors.go | 7 |
2 files changed, 26 insertions, 14 deletions
diff --git a/vendor/github.com/lucasb-eyer/go-colorful/README.md b/vendor/github.com/lucasb-eyer/go-colorful/README.md index c170435..8c89c38 100644 --- a/vendor/github.com/lucasb-eyer/go-colorful/README.md +++ b/vendor/github.com/lucasb-eyer/go-colorful/README.md @@ -124,17 +124,16 @@ Because a `colorful.Color` implements Go's `color.Color` interface (found in the `image/color` package), it can be used anywhere that expects a `color.Color`. Furthermore, you can convert anything that implements the `color.Color` interface -into a `colorful.Color` using the `MakeColorful` function: +into a `colorful.Color` using the `MakeColor` function: ```go -c := colorful.MakeColor(color.Gray16{12345}) +c, ok := colorful.MakeColor(color.Gray16{12345}) ``` -**Caveat:** Be aware that for this latter conversion (using `MakeColor`) hits a corner-case -when alpha is exactly zero. Because `color.Color` uses pre-multiplied alpha colors, -this means the RGB values are lost and it's impossible to recover them. The current -implementation `panic()`s in that case, see [issue 21](https://github.com/lucasb-eyer/go-colorful/issues/21) -for discussion and suggesting alternatives. +**Caveat:** Be aware that this latter conversion (using `MakeColor`) hits a +corner-case when alpha is exactly zero. Because `color.Color` uses pre-multiplied +alpha colors, this means the RGB values are lost (set to 0) and it's impossible +to recover them. In such a case `MakeColor` will return `false` as its second value. ### Comparing colors In the RGB color space, the Euclidian distance between colors *doesn't* correspond @@ -456,16 +455,26 @@ but that is outside the scope of this library. Thanks to [@ZirconiumX](https://github.com/ZirconiumX) for starting this investigation, see [issue #18](https://github.com/lucasb-eyer/go-colorful/issues/18) for details. -### Q: `MakeColor` panics when alpha is zero! -A: Because in that case, the conversion is undefined. See -[issue 21](https://github.com/lucasb-eyer/go-colorful/issues/21) -as well as the short caveat discussion in the ["The `color.Color` interface"](README.md#the-colorcolor-interface) section above. +### Q: Why would `MakeColor` ever fail!? +A: `MakeColor` fails when the alpha channel is zero. In that case, the +conversion is undefined. See [issue 21](https://github.com/lucasb-eyer/go-colorful/issues/21) +as well as the short caveat note in the ["The `color.Color` interface"](README.md#the-colorcolor-interface) +section above. Who? ==== This library has been developed by Lucas Beyer with contributions from -Bastien Dejean (@baskerville) and Phil Kulak (@pkulak). +Bastien Dejean (@baskerville), Phil Kulak (@pkulak) and Christian Muehlhaeuser (@muesli). + +Release Notes +============= + +### Version 1.0 +- API Breaking change in `MakeColor`: instead of `panic`ing when alpha is zero, it now returns a secondary, boolean return value indicating success. See [the color.Color interface](https://github.com/lucasb-eyer/go-colorful#the-colorcolor-interface) section and [this FAQ entry](https://github.com/lucasb-eyer/go-colorful#q-why-would-makecolor-ever-fail) for details. + +### Version 0.9 +- Initial version number after having ignored versioning for a long time :) License: MIT ============ diff --git a/vendor/github.com/lucasb-eyer/go-colorful/colors.go b/vendor/github.com/lucasb-eyer/go-colorful/colors.go index 7469cf7..febf94c 100644 --- a/vendor/github.com/lucasb-eyer/go-colorful/colors.go +++ b/vendor/github.com/lucasb-eyer/go-colorful/colors.go @@ -22,8 +22,11 @@ func (col Color) RGBA() (r, g, b, a uint32) { } // Constructs a colorful.Color from something implementing color.Color -func MakeColor(col color.Color) Color { +func MakeColor(col color.Color) (Color, bool) { r, g, b, a := col.RGBA() + if a == 0 { + return Color{0, 0, 0}, false + } // Since color.Color is alpha pre-multiplied, we need to divide the // RGB values by alpha again in order to get back the original RGB. @@ -34,7 +37,7 @@ func MakeColor(col color.Color) Color { b *= 0xffff b /= a - return Color{float64(r) / 65535.0, float64(g) / 65535.0, float64(b) / 65535.0} + return Color{float64(r) / 65535.0, float64(g) / 65535.0, float64(b) / 65535.0}, true } // Might come in handy sometimes to reduce boilerplate code. |