// +build example jsgo

package main

import (
        "bytes"
        "image"
        _ "image/jpeg"
        "log"

        "github.com/hajimehoshi/ebiten"
        "github.com/hajimehoshi/ebiten/examples/resources/images"
)

const (
        screenWidth  = 320
        screenHeight = 240
)

const mosaicRatio = 16

var (
        gophersImage        *ebiten.Image
        gophersRenderTarget *ebiten.Image
)

func init() {
        // Decode image from a byte slice instead of a file so that
        // this example works in any working directory.
        // If you want to use a file, there are some options:
        // 1) Use os.Open and pass the file to the image decoder.
        //    This is a very regular way, but doesn't work on browsers.
        // 2) Use ebitenutil.OpenFile and pass the file to the image decoder.
        //    This works even on browsers.
        // 3) Use ebitenutil.NewImageFromFile to create an ebiten.Image directly from a file.
        //    This also works on browsers.
        img, _, err := image.Decode(bytes.NewReader(images.Gophers_jpg))
        if err != nil {
                log.Fatal(err)
        }
        gophersImage, _ = ebiten.NewImageFromImage(img, ebiten.FilterDefault)
}

func update(screen *ebiten.Image) error {
        if ebiten.IsRunningSlowly() {
                return nil
        }

        // Shrink the image once.
        op := &ebiten.DrawImageOptions{}
        op.GeoM.Scale(1.0/mosaicRatio, 1.0/mosaicRatio)
        gophersRenderTarget.DrawImage(gophersImage, op)

        // Enlarge the shrunk image.
        // The filter is the nearest filter, so the result will be mosaic.
        op = &ebiten.DrawImageOptions{}
        op.GeoM.Scale(mosaicRatio, mosaicRatio)
        screen.DrawImage(gophersRenderTarget, op)
        return nil
}

func main() {
        w, h := gophersImage.Size()
        gophersRenderTarget, _ = ebiten.NewImage(w/mosaicRatio, h/mosaicRatio, ebiten.FilterDefault)
        if err := ebiten.Run(update, screenWidth, screenHeight, 2, "Mosaic (Ebiten Demo)"); err != nil {
                log.Fatal(err)
        }
}