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histo.go
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histo.go
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// Package histo implements a histogram with persistent save and load features.
package histo
import (
"encoding/gob"
"fmt"
"os"
)
// Histo is a histogram of buddhabrot orbits.
type Histo [][]float64
// New creates a histogram for an image of width * height.
func New(width, height int) Histo {
var h = make(Histo, width)
for i := range h {
h[i] = make([]float64, height)
}
return h
}
// Max finds the highest value in the histogram. Used for color scaling
// algorithms.
func Max(v Histo) (max float64) {
max = -1
for _, row := range v {
for _, v := range row {
if v > max {
max = v
}
}
}
return max
}
// Save saves histograms to a gob file for future re-rendering.
func Save(vs ...Histo) (err error) {
file, err := os.Create("r-g-b.gob")
if err != nil {
return err
}
defer file.Close()
enc := gob.NewEncoder(file)
for _, v := range vs {
err = enc.Encode(v)
if err != nil {
return err
}
}
return nil
}
// Load loads a previously calculated histogram file for re-rendering.
func Load() (r, g, b Histo, err error) {
file, err := os.Open("r-g-b.gob")
if err != nil {
return nil, nil, nil, err
}
defer file.Close()
dec := gob.NewDecoder(file)
if err := dec.Decode(&r); err != nil {
return nil, nil, nil, err
}
if err := dec.Decode(&g); err != nil {
return nil, nil, nil, err
}
if err := dec.Decode(&b); err != nil {
return nil, nil, nil, err
}
return r, g, b, nil
}
func Merge(a, b Histo) (Histo, error) {
if len(a) != len(b) || len(a[0]) != len(b[0]) {
return nil, fmt.Errorf("invalid sizes of histograms: %dx%d != %dx%d", len(a), len(a[0]), len(b), len(b[0]))
}
for y, row := range a {
for x, cell := range row {
b[y][x] += cell
}
}
return b, nil
}