add crop and few helpers

.gitignore

@@ -1,2 +1,2 @@
-
+collage/test_data/
 *jpg

collage/collage.go

@@ -2,6 +2,9 @@
 package collage
 
 import (
+	"errors"
+	"fmt"
+	"image"
 	"io"
 	"io/fs"
 )
@@ -21,6 +24,13 @@ type Rectangle struct {
 	End   Point `json:"end"`
 }
 
+func (r Rectangle) ToImgRect() image.Rectangle {
+	return image.Rectangle{
+		Min: image.Point{int(r.Start.X), int(r.Start.Y)},
+		Max: image.Point{int(r.End.X), int(r.End.Y)},
+	}
+}
+
 type Request struct {
 	BackgroundImage string    `json:"background_image"`
 	Aspect          Dimension `json:"aspect"`
@@ -32,5 +42,31 @@ type Request struct {
 	} `json:"photos"`
 }
 
-func Make(request Request, source fs.FS, output io.Writer) {
+func Make(req Request, source fs.FS, output io.Writer) {
+	rec := image.Rect(0, 0, int(req.Aspect.Width), int(req.Aspect.Height))
+	canvas := image.NewRGBA64(rec)
+	for photo := range req.Photos {
+		fmt.Println(photo)
+	}
+	fmt.Println(canvas)
+}
+
+type HasSubImage interface {
+	SubImage(r image.Rectangle) image.Image
+}
+
+func Crop(img image.Image, r Rectangle) (image.Image, error) {
+	if imgHS, ok := img.(HasSubImage); ok {
+		return imgHS.SubImage(r.ToImgRect()), nil
+	}
+	return nil, errors.New("image does not support cropping")
+}
+
+func GetImage(source fs.FS, imageName string) (image.Image, error) {
+	imgF, err := source.Open(imageName)
+	if err != nil {
+		return nil, err
+	}
+	img, _, err := image.Decode(imgF)
+	return img, err
 }

collage/collage_test.go

@@ -3,22 +3,95 @@ package collage
 import (
 	"embed"
 	"fmt"
+	"image"
+	"image/jpeg"
+	"io"
 	"io/fs"
+	"log"
+	"os"
 	"testing"
 )
 
 //go:embed test_data/*
 var testData embed.FS
 
+var testDataFS fs.FS
+
+func init() {
+	var err error
+	testDataFS, err = fs.Sub(testData, "test_data")
+	if err != nil {
+		log.Panicf("getting test_data subdir failed %v", err)
+	}
+}
+
 func TestMake(t *testing.T) {
 	t.Log("Test was run")
-	ifs, err := fs.Sub(testData, "test_data")
-	if err != nil {
-		t.Fatalf("getting test_data subdir failed %v", err)
-	}
-	img1f, err := ifs.Open("img1.jpg")
+	img1f, err := testDataFS.Open("img1.jpg")
 	if err != nil {
 		t.Fatalf("opening image failed %v", err)
 	}
 	fmt.Printf("%#v\n", img1f)
 }
+
+func TestCrop(t *testing.T) {
+	img, err := GetImage(testDataFS, "img1.jpg")
+	if err != nil {
+		t.Fatalf("failed to get image %v", err)
+	}
+	r := Rectangle{
+		Start: Point{X: 431, Y: 697},
+		End:   Point{X: 2514, Y: 2047},
+	}
+	cropped, err := Crop(img, r)
+	if err != nil {
+		t.Fatalf("failed to crop image %v", err)
+	}
+
+	croppedImgPrefix := fmt.Sprint(cropped)[:1000]
+
+	refPrefixf, err := testDataFS.Open("cropped_image_prefix.txt")
+	if err != nil {
+		t.Fatalf("failed to open ref prefix %v", err)
+	}
+
+	refImgPrefix, err := io.ReadAll(refPrefixf)
+
+	if err != nil {
+		t.Fatalf("failed to read ref prefix %v", err)
+	}
+
+	if string(refImgPrefix) != croppedImgPrefix {
+		t.Fatalf("Cropped image is not the same as reference image")
+	}
+	// SavePrefix(cropped)
+	// expectedImage, err := GetImage(testDataFS, "test_output.jpg")
+	// if err != nil {
+	// 	t.Fatalf("failed to get reference crop image %v", err)
+	// }
+	// fmt.Printf("%v\n", cropped)
+	// fmt.Printf("%v\n", expectedImage)
+	// if fmt.Sprintf("%#v", cropped) != fmt.Sprintf("%#v", expectedImage) {
+	// 	t.Fatalf("Cropped image is not the same as reference image")
+	// }
+	// SaveImage(cropped)
+}
+
+// Save first 1000 bytes of string representation to compare against reference
+func SavePrefix(img image.Image) error {
+	imgStr := fmt.Sprint(img)
+	prefix := imgStr[:1000]
+	return os.WriteFile("./test_data_prefix.txt", []byte(prefix), 0644)
+}
+
+func SaveImage(img image.Image) {
+	out, err := os.Create("./test_output.jpg")
+	if err != nil {
+		fmt.Println(err)
+	}
+
+	var opt jpeg.Options
+	opt.Quality = 100
+
+	jpeg.Encode(out, img, &opt)
+}