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function.go
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function.go
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// seehuhn.de/go/pdf - a library for reading and writing PDF files
// Copyright (C) 2024 Jochen Voss <voss@seehuhn.de>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
package function
import (
"fmt"
"seehuhn.de/go/pdf"
)
// A Func represents a PDF function.
//
// TODO(voss): This is a placeholder for now.
type Func pdf.Object
type Interpolate struct {
XMin, XMax float64
Y0, Y1 []float64
YMin, YMax []float64
Gamma float64
}
func (f *Interpolate) Check() error {
if f.XMin >= f.XMax {
return fmt.Errorf("invalid domain: [%f, %f]", f.XMin, f.XMax)
}
if float64(int(f.Gamma)) != f.Gamma && f.XMin < 0 {
return fmt.Errorf("invalid XMin for non-integer gamma: %f", f.XMin)
}
// TODO(voss): Is 0^0 allowed or not? What is the value?
if f.Gamma < 0 && f.XMin <= 0 && f.XMax >= 0 {
return fmt.Errorf("invalid domain for negative gamma: [%f, %f]", f.XMin, f.XMax)
}
return nil
}