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