First thing is working, it'll pixelate the way I do for the game.

.gitignore

@@ -32,3 +32,4 @@ public
 *.sqlite3
 jankifier
 *.log
+*.png

go.mod

@@ -1,3 +1,5 @@
 module lcthw.dev/go/jankifier
 
 go 1.25.3
+
+require github.com/disintegration/gift v1.2.1

go.sum

@@ -0,0 +1,2 @@
+github.com/disintegration/gift v1.2.1 h1:Y005a1X4Z7Uc+0gLpSAsKhWi4qLtsdEcMIbbdvdZ6pc=
+github.com/disintegration/gift v1.2.1/go.mod h1:Jh2i7f7Q2BM7Ezno3PhfezbR1xpUg9dUg3/RlKGr4HI=

main.go

@@ -1,10 +1,80 @@
 package main
 
 import (
-  "fmt"
+  // "fmt"
+  "os"
+  "image"
+  "log"
+  "image/png"
+  // "image/color"
+  "github.com/disintegration/gift"
+  // "math"
+  "flag"
 )
 
+func LoadImage(filename string) image.Image {
+  reader, err := os.Open(filename)
+  if err != nil { log.Fatal(err) }
+  defer reader.Close()
+
+  img, _, err := image.Decode(reader)
+  if err != nil { log.Fatal(err) }
+
+  return img
+}
+
+func SaveImage(filename string, img image.Image) {
+  out, err := os.Create(filename)
+  if err != nil {
+    log.Fatalf("can't write file %s: %v", filename, err)
+  }
+  defer out.Close()
+
+  err = png.Encode(out, img)
+  if err != nil {
+    log.Fatalf("can't png encode %s: %v", filename, err)
+  }
+}
+
+type Opts struct {
+  InFile string
+  OutFile string
+  PixelWidth int
+}
+
+func ParseOpts() Opts {
+  var opts Opts
+
+  flag.StringVar(&opts.InFile, "input", "", "input file.png")
+  flag.StringVar(&opts.OutFile, "output", "", "output file.png")
+  flag.IntVar(&opts.PixelWidth, "pixel-width", 4, "pixel width")
+  flag.Parse()
+
+  return opts
+}
 
 func main() {
-  fmt.Println("hello")
+  opts := ParseOpts()
+
+  src := LoadImage(opts.InFile)
+  bounds := src.Bounds()
+
+  resize := gift.Resize(bounds.Max.X / opts.PixelWidth, 0, gift.NearestNeighborResampling)
+
+  g := gift.New(resize)
+  smaller := image.NewNRGBA(g.Bounds(bounds))
+  g.Draw(smaller, src)
+
+  upscale := image.NewNRGBA(bounds)
+
+  for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
+    for x := bounds.Min.X; x < bounds.Max.X; x++ {
+      from_x := x / opts.PixelWidth
+      from_y := y / opts.PixelWidth
+      from := smaller.At(from_x, from_y)
+      upscale.Set(x, y, from)
+    }
+  }
+
+  SaveImage(opts.OutFile, upscale)
 }