ebiten/blend.go
Pierre Curto 4de807cc44
all: fix typos (#2558)
Signed-off-by: Pierre Curto <pierre.curto@gmail.com>
2023-01-28 19:06:38 +09:00

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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"
"github.com/hajimehoshi/ebiten/v2/internal/graphicsdriver"
)
// Blend is a blending way of the source color and the destination color.
//
// The final color is calculated like this:
//
// c_src: source RGB values
// c_dst: destination RGB values
// c_out: result RGB values
// α_src: source alpha values
// α_dst: destination alpha values
// α_out: result alpha values
//
// c_out = BlendOperationRGB((BlendFactorSourceRGB) × c_src, (BlendFactorDestinationRGB) × c_dst)
// α_out = BlendOperationAlpha((BlendFactorSourceAlpha) × α_src, (BlendFactorDestinationAlpha) × α_dst)
//
// A blend factor is a factor for source and color destination color values.
// The default is source-over (regular alpha blending).
//
// A blend operation is a binary operator of a source color and a destination color.
// The default is adding.
type Blend struct {
// BlendFactorSourceRGB is a factor for source RGB values.
BlendFactorSourceRGB BlendFactor
// BlendFactorSourceAlpha is a factor for source alpha values.
BlendFactorSourceAlpha BlendFactor
// BlendFactorDestinationRGB is a factor for destination RGB values.
BlendFactorDestinationRGB BlendFactor
// BlendFactorDestinationAlpha is a factor for destination apha values.
BlendFactorDestinationAlpha BlendFactor
// BlendOperationRGB is an operation for source and destination RGB values.
BlendOperationRGB BlendOperation
// BlendOperationAlpha is an operation for source and destination alpha values.
BlendOperationAlpha BlendOperation
}
func (b Blend) internalBlend() graphicsdriver.Blend {
return graphicsdriver.Blend{
BlendFactorSourceRGB: b.BlendFactorSourceRGB.internalBlendFactor(true),
BlendFactorSourceAlpha: b.BlendFactorSourceAlpha.internalBlendFactor(true),
BlendFactorDestinationRGB: b.BlendFactorDestinationRGB.internalBlendFactor(false),
BlendFactorDestinationAlpha: b.BlendFactorDestinationAlpha.internalBlendFactor(false),
BlendOperationRGB: b.BlendOperationRGB.internalBlendOperation(),
BlendOperationAlpha: b.BlendOperationAlpha.internalBlendOperation(),
}
}
// BlendFactor is a factor for source and destination color values.
type BlendFactor byte
const (
// BlendFactorDefault is the default factor value.
// The actual value depends on which source or destination this value is used.
BlendFactorDefault BlendFactor = iota
// BlendFactorZero is a factor:
//
// 0
BlendFactorZero
// BlendFactorOne is a factor:
//
// 1
BlendFactorOne
// BlendFactorSourceColor is a factor:
//
// (source RGBA)
BlendFactorSourceColor
// BlendFactorOneMinusSourceColor is a factor:
//
// 1 - (source color)
BlendFactorOneMinusSourceColor
// BlendFactorSourceAlpha is a factor:
//
// (source alpha)
BlendFactorSourceAlpha
// BlendFactorOneMinusSourceAlpha is a factor:
//
// 1 - (source alpha)
BlendFactorOneMinusSourceAlpha
// BlendFactorDestinationColor is a factor:
//
// (destination RGBA)
BlendFactorDestinationColor
// BlendFactorOneMinusDestinationColor is a factor:
//
// 1 - (destination RGBA)
BlendFactorOneMinusDestinationColor
// BlendFactorDestinationAlpha is a factor:
//
// (destination alpha)
BlendFactorDestinationAlpha
// BlendFactorOneMinusDestinationAlpha is a factor:
//
// 1 - (destination alpha)
BlendFactorOneMinusDestinationAlpha
// TODO: Add BlendFactorSourceAlphaSaturated. This might not work well on some platforms like Steam SDK (#2382).
)
func (b BlendFactor) internalBlendFactor(source bool) graphicsdriver.BlendFactor {
switch b {
case BlendFactorDefault:
// The default is the source-over composition (regular alpha blending).
if source {
return graphicsdriver.BlendFactorOne
}
return graphicsdriver.BlendFactorOneMinusSourceAlpha
case BlendFactorZero:
return graphicsdriver.BlendFactorZero
case BlendFactorOne:
return graphicsdriver.BlendFactorOne
case BlendFactorSourceColor:
return graphicsdriver.BlendFactorSourceColor
case BlendFactorOneMinusSourceColor:
return graphicsdriver.BlendFactorOneMinusSourceColor
case BlendFactorSourceAlpha:
return graphicsdriver.BlendFactorSourceAlpha
case BlendFactorOneMinusSourceAlpha:
return graphicsdriver.BlendFactorOneMinusSourceAlpha
case BlendFactorDestinationColor:
return graphicsdriver.BlendFactorDestinationColor
case BlendFactorOneMinusDestinationColor:
return graphicsdriver.BlendFactorOneMinusDestinationColor
case BlendFactorDestinationAlpha:
return graphicsdriver.BlendFactorDestinationAlpha
case BlendFactorOneMinusDestinationAlpha:
return graphicsdriver.BlendFactorOneMinusDestinationAlpha
default:
panic(fmt.Sprintf("ebiten: invalid blend factor: %d", b))
}
}
// BlendOperation is an operation for source and destination color values.
type BlendOperation byte
const (
// BlendOperationAdd represents adding the source and destination color.
//
// c_out = (BlendFactorSourceRGB) × c_src + (BlendFactorDestinationRGB) × c_dst
// α_out = (BlendFactorSourceAlpha) × α_src + (BlendFactorDestinationAlpha) × α_dst
BlendOperationAdd BlendOperation = iota
// BlendOperationSubtract represents subtracting the source and destination color.
//
// c_out = (BlendFactorSourceRGB) × c_src - (BlendFactorDestinationRGB) × c_dst
// α_out = (BlendFactorSourceAlpha) × α_src - (BlendFactorDestinationAlpha) × α_dst
BlendOperationSubtract
// BlendOperationReverseSubtract represents subtracting the source and destination color in a reversed order.
//
// c_out = (BlendFactorDestinationRGB) × c_dst - (BlendFactorSourceRGB) × c_src
// α_out = (BlendFactorDestinationAlpha) × α_dst - (BlendFactorSourceAlpha) × α_src
BlendOperationReverseSubtract
)
func (b BlendOperation) internalBlendOperation() graphicsdriver.BlendOperation {
switch b {
case BlendOperationAdd:
return graphicsdriver.BlendOperationAdd
case BlendOperationSubtract:
return graphicsdriver.BlendOperationSubtract
case BlendOperationReverseSubtract:
return graphicsdriver.BlendOperationReverseSubtract
default:
panic(fmt.Sprintf("ebiten: invalid blend operation: %d", b))
}
}
// This name convention follows CSS compositing: https://drafts.fxtf.org/compositing-2/.
//
// In the comments,
// c_src, c_dst and c_out represent alpha-premultiplied RGB values of source, destination and output respectively. α_src and α_dst represent alpha values of source and destination respectively.
var (
// BlendSourceOver is a preset Blend for the regular alpha blending.
//
// c_out = c_src + c_dst × (1 - α_src)
// α_out = α_src + α_dst × (1 - α_src)
BlendSourceOver = Blend{
BlendFactorSourceRGB: BlendFactorOne,
BlendFactorSourceAlpha: BlendFactorOne,
BlendFactorDestinationRGB: BlendFactorOneMinusSourceAlpha,
BlendFactorDestinationAlpha: BlendFactorOneMinusSourceAlpha,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendClear is a preset Blend for Porter Duff's 'clear'.
//
// c_out = 0
// α_out = 0
BlendClear = Blend{
BlendFactorSourceRGB: BlendFactorZero,
BlendFactorSourceAlpha: BlendFactorZero,
BlendFactorDestinationRGB: BlendFactorZero,
BlendFactorDestinationAlpha: BlendFactorZero,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendCopy is a preset Blend for Porter Duff's 'copy'.
//
// c_out = c_src
// α_out = α_src
BlendCopy = Blend{
BlendFactorSourceRGB: BlendFactorOne,
BlendFactorSourceAlpha: BlendFactorOne,
BlendFactorDestinationRGB: BlendFactorZero,
BlendFactorDestinationAlpha: BlendFactorZero,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendDestination is a preset Blend for Porter Duff's 'destination'.
//
// c_out = c_dst
// α_out = α_dst
BlendDestination = Blend{
BlendFactorSourceRGB: BlendFactorZero,
BlendFactorSourceAlpha: BlendFactorZero,
BlendFactorDestinationRGB: BlendFactorOne,
BlendFactorDestinationAlpha: BlendFactorOne,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendDestinationOver is a preset Blend for Porter Duff's 'destination-over'.
//
// c_out = c_src × (1 - α_dst) + c_dst
// α_out = α_src × (1 - α_dst) + α_dst
BlendDestinationOver = Blend{
BlendFactorSourceRGB: BlendFactorOneMinusDestinationAlpha,
BlendFactorSourceAlpha: BlendFactorOneMinusDestinationAlpha,
BlendFactorDestinationRGB: BlendFactorOne,
BlendFactorDestinationAlpha: BlendFactorOne,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendSourceIn is a preset Blend for Porter Duff's 'source-in'.
//
// c_out = c_src × α_dst
// α_out = α_src × α_dst
BlendSourceIn = Blend{
BlendFactorSourceRGB: BlendFactorDestinationAlpha,
BlendFactorSourceAlpha: BlendFactorDestinationAlpha,
BlendFactorDestinationRGB: BlendFactorZero,
BlendFactorDestinationAlpha: BlendFactorZero,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendDestinationIn is a preset Blend for Porter Duff's 'destination-in'.
//
// c_out = c_dst × α_src
// α_out = α_dst × α_src
BlendDestinationIn = Blend{
BlendFactorSourceRGB: BlendFactorZero,
BlendFactorSourceAlpha: BlendFactorZero,
BlendFactorDestinationRGB: BlendFactorSourceAlpha,
BlendFactorDestinationAlpha: BlendFactorSourceAlpha,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendSourceOut is a preset Blend for Porter Duff's 'source-out'.
//
// c_out = c_src × (1 - α_dst)
// α_out = α_src × (1 - α_dst)
BlendSourceOut = Blend{
BlendFactorSourceRGB: BlendFactorOneMinusDestinationAlpha,
BlendFactorSourceAlpha: BlendFactorOneMinusDestinationAlpha,
BlendFactorDestinationRGB: BlendFactorZero,
BlendFactorDestinationAlpha: BlendFactorZero,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendDestinationOut is a preset Blend for Porter Duff's 'destination-out'.
//
// c_out = c_dst × (1 - α_src)
// α_out = α_dst × (1 - α_src)
BlendDestinationOut = Blend{
BlendFactorSourceRGB: BlendFactorOneMinusDestinationAlpha,
BlendFactorSourceAlpha: BlendFactorOneMinusDestinationAlpha,
BlendFactorDestinationRGB: BlendFactorZero,
BlendFactorDestinationAlpha: BlendFactorZero,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendSourceAtop is a preset Blend for Porter Duff's 'source-atop'.
//
// c_out = c_src × α_dst + c_dst × (1 - α_src)
// α_out = α_src × α_dst + α_dst × (1 - α_src)
BlendSourceAtop = Blend{
BlendFactorSourceRGB: BlendFactorDestinationAlpha,
BlendFactorSourceAlpha: BlendFactorDestinationAlpha,
BlendFactorDestinationRGB: BlendFactorOneMinusSourceAlpha,
BlendFactorDestinationAlpha: BlendFactorOneMinusSourceAlpha,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendDestinationAtop is a preset Blend for Porter Duff's 'destination-atop'.
//
// c_out = c_src × (1 - α_dst) + c_dst × α_src
// α_out = α_src × (1 - α_dst) + α_dst × α_src
BlendDestinationAtop = Blend{
BlendFactorSourceRGB: BlendFactorOneMinusDestinationAlpha,
BlendFactorSourceAlpha: BlendFactorOneMinusDestinationAlpha,
BlendFactorDestinationRGB: BlendFactorSourceAlpha,
BlendFactorDestinationAlpha: BlendFactorSourceAlpha,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendXor is a preset Blend for Porter Duff's 'xor'.
//
// c_out = c_src × (1 - α_dst) + c_dst × (1 - α_src)
// α_out = α_src × (1 - α_dst) + α_dst × (1 - α_src)
BlendXor = Blend{
BlendFactorSourceRGB: BlendFactorOneMinusDestinationAlpha,
BlendFactorSourceAlpha: BlendFactorOneMinusDestinationAlpha,
BlendFactorDestinationRGB: BlendFactorOneMinusSourceAlpha,
BlendFactorDestinationAlpha: BlendFactorOneMinusSourceAlpha,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
// BlendLighter is a preset Blend for Porter Duff's 'lighter'.
// This is sum of source and destination (a.k.a. 'plus' or 'additive')
//
// c_out = c_src + c_dst
// α_out = α_src + α_dst
BlendLighter = Blend{
BlendFactorSourceRGB: BlendFactorOne,
BlendFactorSourceAlpha: BlendFactorOne,
BlendFactorDestinationRGB: BlendFactorOne,
BlendFactorDestinationAlpha: BlendFactorOne,
BlendOperationRGB: BlendOperationAdd,
BlendOperationAlpha: BlendOperationAdd,
}
)