diff --git a/pkg/dithering/8x8grid.go b/pkg/dithering/8x8grid.go
index bfd6fba..6d311a7 100644
--- a/pkg/dithering/8x8grid.go
+++ b/pkg/dithering/8x8grid.go
@@ -18,16 +18,19 @@ func (_ grid) Bounds() image.Rectangle {
 }
 
 func (g grid) At(x, y int) color.Color {
-	step := int(64 / (g.Gray.Y / 4))
-	if (y*8+x)%step == 0 {
+	n := g.Gray.Y / 4
+	if n == 0 {
 		return color.Black
 	}
-	return color.White
+	step := int(64 / n)
+	if (y*8+x)%step == 0 {
+		return color.White
+	}
+	return color.Black
 }
 
 type uniformGrid struct {
 	image.Image
-	image.Rectangle
 }
 
 func (g uniformGrid) ColorModel() color.Model {
@@ -35,9 +38,23 @@ func (g uniformGrid) ColorModel() color.Model {
 }
 
 func (g uniformGrid) Bounds() image.Rectangle {
-	return g.Rectangle
+	// just need to return something
+	return g.Image.Bounds()
 }
 
 func (g uniformGrid) At(x, y int) color.Color {
-	return color.Color(nil)
+	dx, dy := g.Image.Bounds().Dx(), g.Image.Bounds().Dy()
+	return g.Image.At(x%dx, y%dy)
+}
+
+type Dithering struct {
+	image.Image
+}
+
+func (d Dithering) ColorModel() color.Model { return color.GrayModel }
+func (d Dithering) Bounds() image.Rectangle { return d.Image.Bounds() }
+func (d Dithering) At(x, y int) color.Color {
+	c := color.GrayModel.Convert(d.Image.At(x, y))
+	return uniformGrid{grid{c.(color.Gray)}}.
+		At(x, y)
 }
diff --git a/pkg/dithering/8x8grid_test.go b/pkg/dithering/8x8grid_test.go
index 09200c5..8e300cd 100644
--- a/pkg/dithering/8x8grid_test.go
+++ b/pkg/dithering/8x8grid_test.go
@@ -1,9 +1,11 @@
 package dithering
 
 import (
+	"image"
 	"image/color"
 	"image/png"
 	"math/rand"
+	"os"
 	"os/exec"
 	"testing"
 	"time"
@@ -11,25 +13,61 @@ import (
 	"git.nkpl.cc/twocookedfaggots/imageutils"
 )
 
-func TestGrid(t *testing.T) {
+func init() {
 	rand.Seed(time.Now().UnixNano())
+}
 
+func callImage(img image.Image) {
+	for y := 0; y < img.Bounds().Dy(); y++ {
+		for x := 0; x < img.Bounds().Dx(); x++ {
+			_ = img.At(x, y)
+		}
+	}
+}
+
+func TestGrid(t *testing.T) {
 	command := exec.Command("imv", "-")
 	w, err := command.StdinPipe()
 	if err != nil {
-		t.Error(err)
+		t.Fatal(err)
 	}
-	img := imageutils.Scale(1<<6, grid{color.Gray{uint8(rand.Int() % 64)}})
-
-	go func() {
-		err = png.Encode(w, img)
-		if err != nil {
-			t.Error(err)
-		}
-	}()
-	
 	err = command.Start()
 	if err != nil {
-		t.Error(err)
+		t.Fatal(err)
+	}
+
+	n := uint8(rand.Int() % 256)
+	t.Log(n)
+	img := imageutils.Scale(1<<6, grid{color.Gray{n}})
+	err = png.Encode(w, img)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	callImage(grid{color.Gray{4}})
+	callImage(grid{color.Gray{0}})
+}
+
+func TestDithering(t *testing.T) {
+	r, err := os.Open("/home/potassium/documents/wallpaper/8.png")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer r.Close()
+
+	w, err := os.Create("sample.png")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer w.Close()
+
+	img, err := png.Decode(r)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	err = png.Encode(w, Dithering{img})
+	if err != nil {
+		t.Fatal(err)
 	}
 }
diff --git a/pkg/dithering/cmd/main.go b/pkg/dithering/cmd/main.go
new file mode 100644
index 0000000..6ae3cb7
--- /dev/null
+++ b/pkg/dithering/cmd/main.go
@@ -0,0 +1,15 @@
+package main
+
+import (
+	"git.nkpl.cc/twocookedfaggots/imageutils/pkg/dithering"
+	"git.nkpl.cc/twocookedfaggots/imageutils/util"
+)
+
+func main() {
+	err := util.ProcessStdio(func(img image.Image) image.Image {
+		return dithering.Dithering{img}
+	})
+	if err != nil {
+		panic(err)
+	}
+}
diff --git a/pkg/dithering/sample.png b/pkg/dithering/sample.png
new file mode 100644
index 0000000..bcc389e
Binary files /dev/null and b/pkg/dithering/sample.png differ
diff --git a/pkg/hex.go b/pkg/hex.go
deleted file mode 100644
index 65aa065..0000000
--- a/pkg/hex.go
+++ /dev/null
@@ -1,32 +0,0 @@
-package imageutils
-
-import (
-	"fmt"
-	"image/color"
-	"errors"
-)
-
-var ParseHexColorErr = errors.New("invalid length, must be 7 or 4")
-
-func ParseHexColor(s string) (c color.RGBA, err error) {
-	c.A = 0xff
-	switch len(s) {
-	case 7:
-		_, err = fmt.Sscanf(s, "#%02x%02x%02x", &c.R, &c.G, &c.B)
-	case 4:
-		_, err = fmt.Sscanf(s, "#%1x%1x%1x", &c.R, &c.G, &c.B)
-		// Double the hex digits:
-		c.R *= 17
-		c.G *= 17
-		c.B *= 17
-	default:
-		err = ParseHexColorErr
-
-	}
-	return
-}
-
-func ColorToHex(c color.Color) string {
-	r, g, b, _ := color.NRGBAModel.Convert(c).RGBA()
-	return fmt.Sprintf("#%02x%02x%02x", byte(r), byte(g), byte(b))
-}
diff --git a/pkg/hex_test.go b/pkg/hex_test.go
deleted file mode 100644
index 6a0123c..0000000
--- a/pkg/hex_test.go
+++ /dev/null
@@ -1,47 +0,0 @@
-package imageutils
-
-import (
-	"fmt"
-	"image/png"
-	"os"
-	"path/filepath"
-	"testing"
-)
-
-// Returns path of first occured file
-// with png extension in user's home directory.
-func firstPNG(root string) (filename string,
-	err error) {
-	var fn filepath.WalkFunc = func(path string,
-		info os.FileInfo,
-		fileErr error) error {
-		if fileErr != nil {
-			return fileErr
-		}
-		if !info.IsDir() &&
-			filepath.Ext(path) == ".png" {
-			filename = path
-			return nil
-		}
-		return nil
-	}
-	err = filepath.Walk(root, fn)
-	return
-}
-
-func TestColorToHex(t *testing.T) {
-	root := os.Getenv("HOME")
-	path, err := firstPNG(root)
-	if err != nil {
-		t.Fatal(err)
-	}
-	f, err := os.Open(path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	img, err := png.Decode(f)
-	if err != nil {
-		t.Fatal(err)
-	}
-	fmt.Println(ColorToHex(img.At(0, 0)))
-}
diff --git a/util/stdio.go b/util/stdio.go
new file mode 100644
index 0000000..3b0757b
--- /dev/null
+++ b/util/stdio.go
@@ -0,0 +1,14 @@
+package imageutils
+
+// ProcessImage takes input png image from stdin, processes it with f and outputs it to stdout.
+func ProcessStdio(f func(image.Image) image.Image) {
+      	img, err := png.Decode(os.Stdin)
+	if err != nil {
+		return err
+	}
+	err = png.Encode(os.Stdout, f(img))
+	if err != nil {
+		return err
+	}
+	return err
+}