images: move rescaling from server/image to pkg/images

Fixes http://code.google.com/p/camlistore/issues/detail?id=94

Change-Id: Ifa73e0a3ccbbcaef31ae8870d39f63b8a90aad26

pkg/images/images.go

@@ -21,7 +21,6 @@ import (
 	"fmt"
 	"image"
 	"image/draw"
-	"image/jpeg"
 	"io"
 	"log"
 	"os"
@@ -29,6 +28,7 @@ import (
 	_ "image/gif"
 	_ "image/png"
 
+	"camlistore.org/pkg/misc/resize"
 	"camlistore.org/third_party/github.com/camlistore/goexif/exif"
 )
 
@@ -57,9 +57,18 @@ type DecodeOpts struct {
 	Flip interface{}
 
 	// MaxWidgth and MaxHeight optionally specify bounds on the
-	// final image's size.
+	// image's size. Rescaling is done before flipping or rotating.
+	// Proportions are conserved, so the smallest of the two is used
+	// as the decisive one if needed.
 	MaxWidth, MaxHeight int
 
+	// ScaleWidth and ScaleHeight optionally specify how to rescale the
+	// image's dimensions. Rescaling is done before flipping or rotating.
+	// Proportions are conserved, so the smallest of the two is used
+	// as the decisive one if needed.
+	// They overrule MaxWidth and MaxHeight.
+	ScaleWidth, ScaleHeight float32
+
 	// TODO: consider alternate options if scaled ratio doesn't
 	// match original ratio:
 	//   Crop    bool
@@ -164,6 +173,53 @@ func flip(im image.Image, dir FlipDirection) image.Image {
 	return im
 }
 
+func rescale(im image.Image, opts *DecodeOpts) image.Image {
+	mw, mh := opts.MaxWidth, opts.MaxHeight
+	mwf, mhf := opts.ScaleWidth, opts.ScaleHeight
+	b := im.Bounds()
+	// only do downscaling, otherwise just serve the original image
+	if !opts.wantRescale(b) {
+		return im
+	}
+	// ScaleWidth and ScaleHeight overrule MaxWidth and MaxHeight
+	if mwf > 0.0 && mwf <= 1 {
+		mw = int(mwf * float32(b.Dx()))
+	}
+	if mhf > 0.0 && mhf <= 1 {
+		mh = int(mhf * float32(b.Dy()))
+	}
+
+	const huge = 2400
+	// If it's gigantic, it's more efficient to downsample first
+	// and then resize; resizing will smooth out the roughness.
+	// (trusting the moustachio guys on that one).
+	if b.Dx() > huge || b.Dy() > huge {
+		w, h := mw*2, mh*2
+		if b.Dx() > b.Dy() {
+			w = b.Dx() * h / b.Dy()
+		} else {
+			h = b.Dy() * w / b.Dx()
+		}
+		im = resize.Resample(im, b, w, h)
+		b = im.Bounds()
+	}
+	// conserve proportions. use the smallest of the two as the decisive one.
+	if mw > mh {
+		mw = b.Dx() * mh / b.Dy()
+	} else {
+		mh = b.Dy() * mw / b.Dx()
+	}
+	return resize.Resize(im, b, mw, mh)
+}
+
+func (opts *DecodeOpts) wantRescale(b image.Rectangle) bool {
+	return opts != nil &&
+		(opts.MaxWidth > 0 && opts.MaxWidth < b.Dx() ||
+			opts.MaxHeight > 0 && opts.MaxHeight < b.Dy() ||
+			opts.ScaleWidth > 0.0 && opts.ScaleWidth < float32(b.Dx()) ||
+			opts.ScaleHeight > 0.0 && opts.ScaleHeight < float32(b.Dy()))
+}
+
 func (opts *DecodeOpts) forcedRotate() bool {
 	return opts != nil && opts.Rotate != nil
 }
@@ -195,20 +251,24 @@ func Decode(r io.Reader, opts *DecodeOpts) (image.Image, Config, error) {
 	flipMode := FlipDirection(0)
 	if opts.useEXIF() {
 		ex, err := exif.Decode(tr)
-		if err != nil {
-			imageDebug("No valid EXIF; will not rotate or flip.")
+		maybeRescale := func() (image.Image, Config, error) {
 			im, format, err := image.Decode(io.MultiReader(&buf, r))
+			if err == nil && opts.wantRescale(im.Bounds()) {
+				im = rescale(im, opts)
+				c.Modified = true
+			}
 			c.Format = format
 			c.setBounds(im)
 			return im, c, err
 		}
+		if err != nil {
+			imageDebug("No valid EXIF; will not rotate or flip.")
+			return maybeRescale()
+		}
 		tag, err := ex.Get(exif.Orientation)
 		if err != nil {
 			imageDebug("No \"Orientation\" tag in EXIF; will not rotate or flip.")
-			im, format, err := image.Decode(io.MultiReader(&buf, r))
-			c.Format = format
-			c.setBounds(im)
-			return im, c, err
+			return maybeRescale()
 		}
 		orient := tag.Int(0)
 		switch orient {
@@ -249,16 +309,22 @@ func Decode(r io.Reader, opts *DecodeOpts) (image.Image, Config, error) {
 		}
 	}
 
-	im, err := jpeg.Decode(io.MultiReader(&buf, r))
+	im, format, err := image.Decode(io.MultiReader(&buf, r))
 	if err != nil {
 		return nil, c, err
 	}
+	rescaled := false
+	if opts.wantRescale(im.Bounds()) {
+		im = rescale(im, opts)
+		rescaled = true
+	}
 	im = flip(rotate(im, angle), flipMode)
 	modified := true
-	if angle == 0 && flipMode == 0 {
+	if angle == 0 && flipMode == 0 && !rescaled {
 		modified = false
 	}
-	c.Format = "jpeg"
+
+	c.Format = format
 	c.Modified = modified
 	c.setBounds(im)
 	return im, c, nil

pkg/images/images_test.go

@@ -20,7 +20,7 @@ import (
 	"image"
 	"image/jpeg"
 	"os"
-	"path"
+	"path/filepath"
 	"strings"
 	"testing"
 	"time"
@@ -35,7 +35,7 @@ func equals(im1, im2 image.Image) bool {
 		for x := 0; x < im1.Bounds().Dx(); x++ {
 			r1, g1, b1, a1 := im1.At(x, y).RGBA()
 			r2, g2, b2, a2 := im2.At(x, y).RGBA()
-			if !(r1 == r2 && g1 == g2 && b1 == b2 && a1 == a2) {
+			if r1 != r2 || g1 != g2 || b1 != b2 || a1 != a2 {
 				return false
 			}
 		}
@@ -44,7 +44,20 @@ func equals(im1, im2 image.Image) bool {
 }
 
 func straightFImage(t *testing.T) image.Image {
-	g, err := os.Open(path.Join(datadir, "f1.jpg"))
+	g, err := os.Open(filepath.Join(datadir, "f1.jpg"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer g.Close()
+	straightF, err := jpeg.Decode(g)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return straightF
+}
+
+func smallStraightFImage(t *testing.T) image.Image {
+	g, err := os.Open(filepath.Join(datadir, "f1-s.jpg"))
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -69,14 +82,16 @@ func sampleNames(t *testing.T) []string {
 	return samples
 }
 
-func TestExifCorrection(t *testing.T) {
+// TestEXIFCorrection tests that the input files with EXIF metadata
+// are correctly automatically rotated/flipped when decoded.
+func TestEXIFCorrection(t *testing.T) {
 	samples := sampleNames(t)
 	straightF := straightFImage(t)
 	for _, v := range samples {
-		if !strings.Contains(v, "exif") {
+		if !strings.Contains(v, "exif") || strings.HasSuffix(v, "-s.jpg") {
 			continue
 		}
-		name := path.Join(datadir, v)
+		name := filepath.Join(datadir, v)
 		t.Logf("correcting %s with EXIF Orientation", name)
 		f, err := os.Open(name)
 		if err != nil {
@@ -93,11 +108,17 @@ func TestExifCorrection(t *testing.T) {
 	}
 }
 
+// TestForcedCorrection tests that manually specifying the
+// rotation/flipping to be applied when decoding works as
+// expected.
 func TestForcedCorrection(t *testing.T) {
 	samples := sampleNames(t)
 	straightF := straightFImage(t)
 	for _, v := range samples {
-		name := path.Join(datadir, v)
+		if strings.HasSuffix(v, "-s.jpg") {
+			continue
+		}
+		name := filepath.Join(datadir, v)
 		t.Logf("forced correction of %s", name)
 		f, err := os.Open(name)
 		if err != nil {
@@ -137,10 +158,61 @@ func TestForcedCorrection(t *testing.T) {
 	}
 }
 
+// TestRescale verifies that rescaling an image, without
+// any rotation/flipping, produces the expected image.
+func TestRescale(t *testing.T) {
+	name := filepath.Join(datadir, "f1.jpg")
+	t.Logf("rescaling %s with half-width and half-height", name)
+	f, err := os.Open(name)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	rescaledIm, _, err := Decode(f, &DecodeOpts{ScaleWidth: 0.5, ScaleHeight: 0.5})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	smallIm := smallStraightFImage(t)
+
+	if !equals(rescaledIm, smallIm) {
+		t.Fatalf("%v not properly rescaled", name)
+	}
+}
+
+// TestRescaleEXIF verifies that rescaling an image, followed
+// by the automatic EXIF correction (rotation/flipping),
+// produces the expected image. All the possible correction
+// modes are tested.
+func TestRescaleEXIF(t *testing.T) {
+	smallStraightF := smallStraightFImage(t)
+	samples := sampleNames(t)
+	for _, v := range samples {
+		if !strings.Contains(v, "exif") {
+			continue
+		}
+		name := filepath.Join(datadir, v)
+		t.Logf("rescaling %s with half-width and half-height", name)
+		f, err := os.Open(name)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer f.Close()
+		rescaledIm, _, err := Decode(f, &DecodeOpts{ScaleWidth: 0.5, ScaleHeight: 0.5})
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if !equals(rescaledIm, smallStraightF) {
+			t.Fatalf("%v not properly rescaled", name)
+		}
+	}
+}
+
 // TODO(mpl): move this test to the goexif lib if/when we contribute
 // back the DateTime stuff to upstream.
 func TestDateTime(t *testing.T) {
-	f, err := os.Open(path.Join(datadir, "f1-exif.jpg"))
+	f, err := os.Open(filepath.Join(datadir, "f1-exif.jpg"))
 	if err != nil {
 		t.Fatal(err)
 	}

pkg/server/image.go

@@ -33,7 +33,6 @@ import (
 	"camlistore.org/pkg/blobserver"
 	"camlistore.org/pkg/images"
 	"camlistore.org/pkg/magic"
-	"camlistore.org/pkg/misc/resize"
 	"camlistore.org/pkg/schema"
 )
 
@@ -149,8 +148,6 @@ func (ih *ImageHandler) scaledCached(buf *bytes.Buffer, file *blobref.BlobRef) (
 }
 
 func (ih *ImageHandler) scaleImage(buf *bytes.Buffer, file *blobref.BlobRef) (format string, err error) {
-	mw, mh := ih.MaxWidth, ih.MaxHeight
-
 	fr, err := schema.NewFileReader(ih.storageSeekFetcher(), file)
 	if err != nil {
 		return format, err
@@ -161,7 +158,8 @@ func (ih *ImageHandler) scaleImage(buf *bytes.Buffer, file *blobref.BlobRef) (fo
 	if err != nil {
 		return format, fmt.Errorf("image resize: error reading image %s: %v", file, err)
 	}
-	i, imConfig, err := images.Decode(bytes.NewReader(buf.Bytes()), nil)
+	i, imConfig, err := images.Decode(bytes.NewReader(buf.Bytes()),
+		&images.DecodeOpts{MaxWidth: ih.MaxWidth, MaxHeight: ih.MaxHeight})
 	if err != nil {
 		return format, err
 	}
@@ -176,34 +174,7 @@ func (ih *ImageHandler) scaleImage(buf *bytes.Buffer, file *blobref.BlobRef) (fo
 		b = i.Bounds()
 	}
 
-	// only do downscaling, otherwise just serve the original image
-	if mw < b.Dx() || mh < b.Dy() {
-		useBytesUnchanged = false
-
-		const huge = 2400
-		// If it's gigantic, it's more efficient to downsample first
-		// and then resize; resizing will smooth out the roughness.
-		// (trusting the moustachio guys on that one).
-		if b.Dx() > huge || b.Dy() > huge {
-			w, h := mw*2, mh*2
-			if b.Dx() > b.Dy() {
-				w = b.Dx() * h / b.Dy()
-			} else {
-				h = b.Dy() * w / b.Dx()
-			}
-			i = resize.Resample(i, i.Bounds(), w, h)
-			b = i.Bounds()
-		}
-		// conserve proportions. use the smallest of the two as the decisive one.
-		if mw > mh {
-			mw = b.Dx() * mh / b.Dy()
-		} else {
-			mh = b.Dy() * mw / b.Dx()
-		}
-	}
-
 	if !useBytesUnchanged {
-		i = resize.Resize(i, b, mw, mh)
 		// Encode as a new image
 		buf.Reset()
 		switch format {