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curve.go
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curve.go
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// Copyright (C) 2017 Google Inc.
//
// 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 stream
import (
"bytes"
"fmt"
"math"
"github.com/google/gapid/core/data/endian"
"github.com/google/gapid/core/os/device"
)
func (m *mapping) transform(count int, f func(float64) float64) error {
data := make([]byte, 8*count)
tmp := mapping{
src: m.src,
dst: buf{
bytes: data,
component: &Component{
DataType: &F64,
Sampling: m.src.component.GetSampling(),
Channel: m.src.component.GetChannel(),
},
stride: 64,
},
}
if err := tmp.conv(count); err != nil {
return err
}
r := endian.Reader(bytes.NewReader(data), device.LittleEndian)
w := endian.Writer(bytes.NewBuffer(data[:0]), device.LittleEndian)
for i := 0; i < count; i++ {
w.Float64(f(r.Float64()))
}
m.src = tmp.dst
return nil
}
func (m *mapping) convertCurve(count int) error {
src := m.src.component.GetSampling().GetCurve()
dst := m.dst.component.GetSampling().GetCurve()
switch {
case src == dst:
return nil
case src == Curve_sRGB && dst == Curve_Linear:
if err := m.transform(count, func(v float64) float64 {
if v <= 0.04045 {
return v / 12.92
}
return math.Pow((v+0.055)/1.055, 2.4)
}); err != nil {
return err
}
m.src = m.src.clone()
m.src.component.Sampling.Curve = Curve_Linear
return nil
case src == Curve_Linear && dst == Curve_sRGB:
if err := m.transform(count, func(v float64) float64 {
if v <= 0.0031308 {
return v * 12.92
}
return 1.055*math.Pow(v, 1.0/2.4) - 0.055
}); err != nil {
return err
}
m.src = m.src.clone()
m.src.component.Sampling.Curve = Curve_sRGB
return nil
}
return fmt.Errorf("Cannot convert curve from %v to %v", src, dst)
}