package main

import (
  "math"
  "image"
  "image/draw"
  "image/jpeg"
  "image/png"
  "path/filepath"
  "strings"
  "fmt"
  "os"
)

func avgColor(orig, upd int) int {
  a := float64(orig * orig)
  b := float64(upd * upd)
  return int(math.Sqrt((a + b)/2))
}

func loadImage(path string) (*image.RGBA, string) {
  f, err := os.Open(path)
  defer f.Close()
  if err != nil {
    panic(fmt.Sprintf("File access error: Unable to open image at path %q", path))
  }
  img, format, err := image.Decode(f)
  rect := img.Bounds()
  rgba := image.NewRGBA(rect)
  draw.Draw(rgba, rect, img, rect.Min, draw.Src)

  return rgba, format 
}

func saveImage(iPath, filterName, encodeType string, img *image.RGBA) {
  ext := filepath.Ext(iPath)
  name := strings.TrimSuffix(filepath.Base(iPath), ext)
  newImagePath := fmt.Sprintf("%s/%s_%s%s", filepath.Dir(iPath), name, filterName, ext)
  fg, err := os.Create(newImagePath)
  defer fg.Close()
  if err != nil {
    panic(fmt.Sprintf("File access error: Unable to save image to path %q", newImagePath))
  }

  if encodeType == "jpeg" {
    err = jpeg.Encode(fg, img, nil)
    if err != nil {
      panic("Encode error: Unable to encode output as jpeg")
    }
  } else if encodeType == "png" {
    err = png.Encode(fg, img)
    if err != nil {
      panic("Encode error: Unable to encode output as png")
    }
  } else {
    panic(fmt.Sprintf("Encode error: Unable to encode output to unsupported format %q", encodeType))
  }
}