//----------------------------------------
//
// Copyright © ying32. All Rights Reserved.
//
// Licensed under Apache License 2.0
//
//----------------------------------------

package main

import (
	"image"
	"image/color"
	"log"
	"os"

	"github.com/disintegration/gift"
)

func loadImage(filename string) image.Image {
	f, err := os.Open(filename)
	if err != nil {
		log.Fatalf("os.Open failed: %v", err)
	}
	defer f.Close()
	img, _, err := image.Decode(f)
	if err != nil {
		log.Fatalf("image.Decode failed: %v", err)
	}
	return img
}

var (
	filters = map[string]gift.Filter{
		"resize":              gift.Resize(100, 0, gift.LanczosResampling),
		"crop_to_size":        gift.CropToSize(100, 100, gift.LeftAnchor),
		"rotate_180":          gift.Rotate180(),
		"rotate_30":           gift.Rotate(30, color.Transparent, gift.CubicInterpolation),
		"brightness_increase": gift.Brightness(30),
		"brightness_decrease": gift.Brightness(-30),
		"contrast_increase":   gift.Contrast(30),
		"contrast_decrease":   gift.Contrast(-30),
		"saturation_increase": gift.Saturation(50),
		"saturation_decrease": gift.Saturation(-50),
		"gamma_1.5":           gift.Gamma(1.5),
		"gamma_0.5":           gift.Gamma(0.5),
		"gaussian_blur":       gift.GaussianBlur(1),
		"unsharp_mask":        gift.UnsharpMask(1, 1, 0),
		"sigmoid":             gift.Sigmoid(0.5, 7),
		"pixelate":            gift.Pixelate(5),
		"colorize":            gift.Colorize(240, 50, 100),
		"grayscale":           gift.Grayscale(),
		"sepia":               gift.Sepia(100),
		"invert":              gift.Invert(),
		"mean":                gift.Mean(5, true),
		"median":              gift.Median(5, true),
		"minimum":             gift.Minimum(5, true),
		"maximum":             gift.Maximum(5, true),
		"hue_rotate":          gift.Hue(45),
		"color_balance":       gift.ColorBalance(10, -10, -10),
		"color_func": gift.ColorFunc(
			func(r0, g0, b0, a0 float32) (r, g, b, a float32) {
				r = 1 - r0   // invert the red channel
				g = g0 + 0.1 // shift the green channel by 0.1
				b = 0        // set the blue channel to 0
				a = a0       // preserve the alpha channel
				return r, g, b, a
			},
		),
		"convolution_emboss": gift.Convolution(
			[]float32{
				-1, -1, 0,
				-1, 1, 1,
				0, 1, 1,
			},
			false, false, false, 0.0,
		),
	}
)