feat(image): implement processor options

image/compress.go

@@ -4,27 +4,48 @@ import "image"
 
 // Compressor compresses images.
 type Compressor struct {
-	compressor CompressionFunc
+	compressor       CompressionFunc
+	compressOriginal bool
 }
 
 // CompressionFunc is the actual implementation of a compressor.
 // Available implementations:
 //   - [github.com/modernice/media-tools/image/compressor.JPEG]
 type CompressionFunc func(image.Image) (*image.NRGBA, error)
 
+// CompressorOption is an option for a [*Compressor].
+type CompressorOption func(*Compressor)
+
+// CompressOriginal returns a CompressorOption that enables compression of
+// the original image of a [Pipeline]. By default, the original image will not
+// be compressed and instead returned as is to preserve the original image
+// quality.
+func CompressOriginal(v bool) CompressorOption {
+	return func(c *Compressor) {
+		c.compressOriginal = v
+	}
+}
+
 // Compress returns a [*Compressor] that compresses images using the provided
 // [CompressionFunc].
-func Compress(compressor CompressionFunc) *Compressor {
-	return &Compressor{compressor: compressor}
+func Compress(compressor CompressionFunc, opts ...CompressorOption) *Compressor {
+	c := &Compressor{compressor: compressor}
+	for _, opt := range opts {
+		opt(c)
+	}
+	return c
 }
 
 // Compress compresses an image using the configured [CompressionFunc].
 func (c *Compressor) Compress(img image.Image) (*image.NRGBA, error) {
 	return c.compressor(img)
 }
 
+// Process implements [Processor]. By default, the original image will not be
+// compressed and returned as is to preserve quality. To also compress the
+// original image, pass the [CompressOriginal] option to [Compress].
 func (c *Compressor) Process(ctx ProcessorContext) ([]*image.NRGBA, error) {
-	if ctx.Original() {
+	if !c.compressOriginal && ctx.Original() {
 		return []*image.NRGBA{ctx.Image()}, nil
 	}
 

image/compress_test.go

@@ -2,13 +2,15 @@ package image_test
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	stdimage "image"
 	"image/jpeg"
 	"testing"
 
 	"github.com/modernice/media-tools/image"
 	"github.com/modernice/media-tools/image/compressor"
+	"github.com/modernice/media-tools/image/internal"
 )
 
 func TestCompressor_Compress(t *testing.T) {
@@ -42,6 +44,64 @@ func TestCompressor_Compress(t *testing.T) {
 	}
 }
 
+func TestCompressor_Process_original(t *testing.T) {
+	compressor := image.Compress(compressor.JPEG(50))
+
+	original := newExample()
+	ctx := image.NewProcessorContext(context.Background(), original, true)
+
+	compressed, err := compressor.Process(ctx)
+	if err != nil {
+		t.Fatalf("run processor: %v", err)
+	}
+
+	if len(compressed) != 1 {
+		t.Fatalf("expected 1 compressed image; got %d", len(compressed))
+	}
+
+	orgSize, err := internal.SizeOf(original)
+	if err != nil {
+		t.Fatalf("get original size: %v", err)
+	}
+	compressedSize, err := internal.SizeOf(compressed[0])
+	if err != nil {
+		t.Fatalf("get compressed size: %v", err)
+	}
+
+	if orgSize != compressedSize {
+		t.Fatalf("original image should not be compressed")
+	}
+}
+
+func TestCompressor_Process_CompressOriginal(t *testing.T) {
+	compressor := image.Compress(compressor.JPEG(50), image.CompressOriginal(true))
+
+	original := newExample()
+	ctx := image.NewProcessorContext(context.Background(), original, true)
+
+	compressed, err := compressor.Process(ctx)
+	if err != nil {
+		t.Fatalf("run processor: %v", err)
+	}
+
+	if len(compressed) != 1 {
+		t.Fatalf("expected 1 compressed image; got %d", len(compressed))
+	}
+
+	orgSize, err := internal.SizeOf(original)
+	if err != nil {
+		t.Fatalf("get original size: %v", err)
+	}
+	compressedSize, err := internal.SizeOf(compressed[0])
+	if err != nil {
+		t.Fatalf("get compressed size: %v", err)
+	}
+
+	if orgSize == compressedSize {
+		t.Fatalf("original image should be compressed when providing the CompressOriginal(true) option")
+	}
+}
+
 func getImageSize(t *testing.T, img stdimage.Image) int {
 	var buf bytes.Buffer
 	if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 100}); err != nil {

image/internal/internal.go

@@ -0,0 +1,40 @@
+package internal
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/draw"
+	"image/jpeg"
+
+	"github.com/vitali-fedulov/images4"
+)
+
+// ToNRGBA converts an image.Image to an [*image.NRGBA].
+func ToNRGBA(img image.Image) *image.NRGBA {
+	out := image.NewNRGBA(img.Bounds())
+	draw.Draw(out, out.Bounds(), img, image.Point{}, draw.Src)
+	return out
+}
+
+// SameImages returns whether two images are identical. The images are allowed
+// to have different bounds and still be the same.
+func SameImages(a, b image.Image) bool {
+	iconA := images4.Icon(a)
+	iconB := images4.Icon(b)
+	return images4.Similar(iconA, iconB)
+}
+
+// EqualImages returns whether two images are identical, including theirs bounds.
+func EqualImages(a, b image.Image) bool {
+	return a.Bounds() == b.Bounds() && SameImages(a, b)
+}
+
+// SizeOf returns the JPEG size of an image in bytes.
+func SizeOf(img image.Image) (int, error) {
+	var buf bytes.Buffer
+	if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 100}); err != nil {
+		return 0, fmt.Errorf("encode as JPEG: %w", err)
+	}
+	return buf.Len(), nil
+}

image/pipeline.go

@@ -45,6 +45,15 @@ type ProcessorContext interface {
 	Original() bool
 }
 
+// NewProcessorContext returns a new [ProcessorContext] for a [Processor].
+func NewProcessorContext(ctx context.Context, img *image.NRGBA, original bool) ProcessorContext {
+	return &processorContext{
+		Context:  ctx,
+		image:    img,
+		original: original,
+	}
+}
+
 type processorContext struct {
 	context.Context
 
@@ -73,17 +82,14 @@ func (pipeline Pipeline) Run(ctx context.Context, img image.Image) (PipelineResu
 
 	previous := []*image.NRGBA{nimg}
 
-	for _, processor := range pipeline {
+	for i, processor := range pipeline {
 		_previous := previous
 		previous = previous[:0]
 
 		for _, img := range _previous {
-			pctx := processorContext{
-				Context: ctx,
-				image:   img,
-			}
+			pctx := NewProcessorContext(ctx, img, i == 0)
 
-			processed, err := processor.Process(&pctx)
+			processed, err := processor.Process(pctx)
 			if err != nil {
 				return PipelineResult{}, fmt.Errorf("%T processor: %w", processor, err)
 			}

image/pipeline_test.go

@@ -2,13 +2,12 @@ package image_test
 
 import (
 	"context"
-	stdimage "image"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/modernice/media-tools/image"
 	"github.com/modernice/media-tools/image/compressor"
-	"github.com/vitali-fedulov/images4"
+	"github.com/modernice/media-tools/image/internal"
 )
 
 func TestPipeline(t *testing.T) {
@@ -37,13 +36,7 @@ func TestPipeline(t *testing.T) {
 		}
 	}
 
-	if !equalImages(original, result.Images[0].Image) {
+	if !internal.SameImages(original, result.Images[0].Image) {
 		t.Fatalf("first image should be the original\n%s", cmp.Diff(original, result.Images[0].Image))
 	}
 }
-
-func equalImages(a, b stdimage.Image) bool {
-	iconA := images4.Icon(a)
-	iconB := images4.Icon(b)
-	return images4.Similar(iconA, iconB)
-}

image/resize.go

@@ -8,8 +8,15 @@ import (
 
 // Resizer resizes images to a set of dimensions.
 type Resizer struct {
-	dimensions []Dimensions
-	filter     imaging.ResampleFilter
+	dimensions      []Dimensions
+	filter          imaging.ResampleFilter
+	discardOriginal bool
+}
+
+// DimensionProvider provides image dimensions to Resizer. DimensionProvider is
+// implemented by [DimensionList] and [DimensionMap].
+type DimensionProvider interface {
+	Dimensions() []Dimensions
 }
 
 // ResizerOption is an option for a Resizer.
@@ -23,10 +30,12 @@ func ResampleFilter(filter imaging.ResampleFilter) ResizerOption {
 	}
 }
 
-// DimensionProvider provides image dimensions to Resizer. DimensionProvider is
-// implemented by [DimensionList] and [DimensionMap].
-type DimensionProvider interface {
-	Dimensions() []Dimensions
+// DiscardOriginal returns a ResizerOption that discards the original image when
+// executed in a [Pipeline].
+func DiscardOriginal(v bool) ResizerOption {
+	return func(r *Resizer) {
+		r.discardOriginal = v
+	}
 }
 
 // Resize returns a Resizer that resizes images to the given dimensions.
@@ -39,7 +48,8 @@ func Resize(dimensions DimensionProvider, opts ...ResizerOption) *Resizer {
 	return r
 }
 
-// Resize resizes an image to the configured dimensinos.
+// Resize resizes an image to the configured dimensinos. The input image is not
+// returned in the result.
 func (r *Resizer) Resize(img image.Image) ([]*image.NRGBA, error) {
 	resized := make([]*image.NRGBA, len(r.dimensions))
 	for i, dim := range r.dimensions {
@@ -52,10 +62,17 @@ func (r *Resizer) resize(img image.Image, dim Dimensions) *image.NRGBA {
 	return imaging.Resize(img, dim.Width(), dim.Height(), r.filter)
 }
 
+// Process implements [Processor]. The input image is returned in the result as
+// the first element.
 func (r *Resizer) Process(ctx ProcessorContext) ([]*image.NRGBA, error) {
 	resized, err := r.Resize(ctx.Image())
 	if err != nil {
 		return nil, err
 	}
+
+	if r.discardOriginal {
+		return resized, nil
+	}
+
 	return append([]*image.NRGBA{ctx.Image()}, resized...), nil
 }

image/resize_test.go

@@ -1,12 +1,14 @@
 package image_test
 
 import (
+	"context"
 	_ "embed"
 	"fmt"
 	stdimage "image"
 	"testing"
 
 	"github.com/modernice/media-tools/image"
+	"github.com/modernice/media-tools/image/internal"
 )
 
 func TestResizer_Resize_DimensionList(t *testing.T) {
@@ -47,6 +49,50 @@ func TestResizer_Resize_DimensionList(t *testing.T) {
 	}
 }
 
+func TestResizer_Process(t *testing.T) {
+	dimensions := image.DimensionList{{360}, {640}, {960}}
+
+	resizer := image.Resize(dimensions)
+
+	original := newExample()
+	ctx := image.NewProcessorContext(context.Background(), original, true)
+
+	resized, err := resizer.Process(ctx)
+	if err != nil {
+		t.Fatalf("run processor: %v", err)
+	}
+
+	if len(resized) != len(dimensions)+1 {
+		t.Fatalf("expected %d resized images (including the original); got %d", len(dimensions)+1, len(resized))
+	}
+
+	if !internal.EqualImages(original, resized[0]) {
+		t.Fatalf("first returned image should be the original")
+	}
+}
+
+func TestResizer_Process_DiscardOriginal(t *testing.T) {
+	dimensions := image.DimensionList{{360}, {640}, {960}}
+
+	resizer := image.Resize(dimensions, image.DiscardOriginal(true))
+
+	original := newExample()
+	ctx := image.NewProcessorContext(context.Background(), original, true)
+
+	resized, err := resizer.Process(ctx)
+	if err != nil {
+		t.Fatalf("run processor: %v", err)
+	}
+
+	if len(resized) != len(dimensions) {
+		t.Fatalf("expected %d resized images (excluding the original); got %d", len(dimensions), len(resized))
+	}
+
+	if internal.EqualImages(original, resized[0]) {
+		t.Fatalf("original image should not be returned")
+	}
+}
+
 func saveResized(t *testing.T, dim image.Dimensions, img *stdimage.NRGBA) {
 	saveOutImage(t, fmt.Sprintf("resized-%dx%d.jpg", dim.Width(), dim.Height()), dim, img)
 }