package vision

import (
	"image"
	"image/color"
	"math"

	"github.com/disintegration/imaging"
	"github.com/fogleman/gg"
)

// Sepia 应用怀旧滤镜
func (c *Canvas) Sepia() {
	img := c.dc.Image()
	bounds := img.Bounds()
	w, h := bounds.Dx(), bounds.Dy()
	result := image.NewRGBA(bounds)

	for y := 0; y < h; y++ {
		for x := 0; x < w; x++ {
			r, g, b, a := img.At(x, y).RGBA()
			r8, g8, b8 := float64(r>>8), float64(g>>8), float64(b>>8)

			tr := 0.393*r8 + 0.769*g8 + 0.189*b8
			tg := 0.349*r8 + 0.686*g8 + 0.168*b8
			tb := 0.272*r8 + 0.534*g8 + 0.131*b8

			if tr > 255 { tr = 255 }
			if tg > 255 { tg = 255 }
			if tb > 255 { tb = 255 }

			result.SetRGBA(x, y, color.RGBA{uint8(tr), uint8(tg), uint8(tb), uint8(a >> 8)})
		}
	}
	c.dc = gg.NewContextForImage(result)
}

// Pixelate 像素化处理
func (c *Canvas) Pixelate(size int) {
	if size <= 1 { return }
	img := c.dc.Image()
	bounds := img.Bounds()
	w, h := bounds.Dx(), bounds.Dy()
	
	// 先缩小再放大实现像素化
	small := imaging.Resize(img, w/size, h/size, imaging.NearestNeighbor)
	pixelated := imaging.Resize(small, w, h, imaging.NearestNeighbor)
	
	c.dc = gg.NewContextForImage(pixelated)
}

// Vignette 应用暗角效果
func (c *Canvas) Vignette(intensity float64) {
	w, h := float64(c.Width()), float64(c.Height())
	cx, cy := w/2, h/2
	maxDist := math.Sqrt(cx*cx + cy*cy)

	c.dc.Push()
	for y := 0.0; y < h; y += 2 {
		for x := 0.0; x < w; x += 2 {
			dist := math.Sqrt((x-cx)*(x-cx) + (y-cy)*(y-cy))
			factor := 1.0 - (dist/maxDist)*intensity
			if factor < 0 { factor = 0 }
			
			r, g, b, a := c.dc.Image().At(int(x), int(y)).RGBA()
			c.dc.SetColor(color.RGBA{
				R: uint8(float64(r>>8) * factor),
				G: uint8(float64(g>>8) * factor),
				B: uint8(float64(b>>8) * factor),
				A: uint8(a >> 8),
			})
			c.dc.SetPixel(int(x), int(y))
			c.dc.SetPixel(int(x+1), int(y))
			c.dc.SetPixel(int(x), int(y+1))
			c.dc.SetPixel(int(x+1), int(y+1))
		}
	}
	c.dc.Pop()
}