ebiten/colorscale.go

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// Copyright 2022 The Ebitengine Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ebiten
import (
"fmt"
"image/color"
)
// ColorScale represents a scale of RGBA color.
// ColorScale is intended to be applied to a premultiplied-alpha color value.
//
// The initial (zero) value of ColorScale is an identity scale (1, 1, 1, 1).
type ColorScale struct {
// These values are adjusted by -1 from the actual values.
// It's because the initial value should be 1 instead of 0.
r_1, g_1, b_1, a_1 float32
}
// String returns a string representing the color scale.
func (c *ColorScale) String() string {
return fmt.Sprintf("(%f,%f,%f,%f)", c.r_1+1, c.g_1+1, c.b_1+1, c.a_1+1)
}
// Reset resets the ColorScale as identity.
func (c *ColorScale) Reset() {
c.r_1 = 0
c.g_1 = 0
c.b_1 = 0
c.a_1 = 0
}
// R returns the red scale.
func (c *ColorScale) R() float32 {
return c.r_1 + 1
}
// G returns the green scale.
func (c *ColorScale) G() float32 {
return c.g_1 + 1
}
// B returns the blue scale.
func (c *ColorScale) B() float32 {
return c.b_1 + 1
}
// A returns the alpha scale.
func (c *ColorScale) A() float32 {
return c.a_1 + 1
}
func (c *ColorScale) elements() (float32, float32, float32, float32) {
return c.r_1 + 1, c.g_1 + 1, c.b_1 + 1, c.a_1 + 1
}
// SetR overwrites the current red value with r.
func (c *ColorScale) SetR(r float32) {
c.r_1 = r - 1
}
// SetG overwrites the current green value with g.
func (c *ColorScale) SetG(g float32) {
c.g_1 = g - 1
}
// SetB overwrites the current blue value with b.
func (c *ColorScale) SetB(b float32) {
c.b_1 = b - 1
}
// SetA overwrites the current alpha value with a.
func (c *ColorScale) SetA(a float32) {
c.a_1 = a - 1
}
// Scale multiplies the given values to the current scale.
func (c *ColorScale) Scale(r, g, b, a float32) {
c.r_1 = (c.r_1+1)*r - 1
c.g_1 = (c.g_1+1)*g - 1
c.b_1 = (c.b_1+1)*b - 1
c.a_1 = (c.a_1+1)*a - 1
}
// ScaleAlpha multiplies the given alpha value to the current scale.
func (c *ColorScale) ScaleAlpha(a float32) {
c.r_1 = (c.r_1+1)*a - 1
c.g_1 = (c.g_1+1)*a - 1
c.b_1 = (c.b_1+1)*a - 1
c.a_1 = (c.a_1+1)*a - 1
}
// ScaleWithColor multiplies the given color values to the current scale.
func (c *ColorScale) ScaleWithColor(clr color.Color) {
cr, cg, cb, ca := clr.RGBA()
c.Scale(float32(cr)/0xffff, float32(cg)/0xffff, float32(cb)/0xffff, float32(ca)/0xffff)
}
func (c *ColorScale) apply(r, g, b, a float32) (float32, float32, float32, float32) {
return (c.r_1 + 1) * r, (c.g_1 + 1) * g, (c.b_1 + 1) * b, (c.a_1 + 1) * a
}