Serve and accept JPEG XL as an image format (part of #222)

A JPEG XL source is accepted, and orig of one is JPEG XL. The format
jxl works in plain and encrypted URLs and on the generator page,
served as image/jxl; auto chooses it first when Accept names
image/jxl.

govips sends libvips a JPEG XL distance, which overrides the quality,
so q becomes a distance, keeping 100 lossy. Metadata is removed from
the image before the JPEG XL save, as govips cannot have libvips strip
it, and the image is given 72 dpi so that the EXIF block libvips 8.16
adds holds nothing from the source. The sRGB conversion moved ahead of
the format switch, and a CMYK image with no ICC profile is converted
to sRGB, as libvips cannot save CMYK as JPEG XL.

Model: opus-5-5

internal/handlers/format_auto.go

@@ -14,8 +14,8 @@ import (
 // Errors for an Accept header that an auto URL cannot be served for.
 var (
 	errInvalidAccept = errors.New("invalid Accept header")
-	errNotAcceptable = errors.New(
-		"not acceptable: auto serves image/avif, image/webp or image/jpeg")
+	errNotAcceptable = errors.New("not acceptable: auto serves " +
+		"image/jxl, image/avif, image/webp or image/jpeg")
 )
 
 // chooseAutoFormat replaces the format auto in req with the format
@@ -51,11 +51,11 @@ func (s *Handlers) chooseAutoFormat(
 }
 
 // formatForAccept returns the format an auto URL is served in for the Accept
-// header accept: AVIF when it names image/avif, else WebP when it names
-// image/webp, else JPEG when its most specific entry of image/jpeg, image/*
-// and */* allows it, or when it names nothing. A q of 0 refuses a format.
-// AVIF and WebP must be named, as clients that cannot show them send image/*
-// and */* too.
+// header accept: JPEG XL when it names image/jxl, else AVIF when it names
+// image/avif, else WebP when it names image/webp, else JPEG when its most
+// specific entry of image/jpeg, image/* and */* allows it, or when it names
+// nothing. A q of 0 refuses a format. JPEG XL, AVIF and WebP must be named, as
+// clients that cannot show them send image/* and */* too.
 func formatForAccept(accept string) (imgcache.ImageFormat, error) {
 	qualities, err := parseAccept(accept)
 	if err != nil {
@@ -66,6 +66,10 @@ func formatForAccept(accept string) (imgcache.ImageFormat, error) {
 		return imgcache.FormatJPEG, nil
 	}
 
+	if qualities["image/jxl"] > 0 {
+		return imgcache.FormatJXL, nil
+	}
+
 	if qualities["image/avif"] > 0 {
 		return imgcache.FormatAVIF, nil
 	}

internal/handlers/jpegxl_internal_test.go

@@ -0,0 +1,73 @@
+package handlers
+
+import (
+	"log/slog"
+	"net/http"
+	"testing"
+
+	"github.com/davidbyttow/govips/v2/vips"
+
+	"sneak.berlin/go/pixa/internal/imgcache"
+)
+
+// jxlType is the content type of JPEG XL.
+const jxlType = "image/jxl"
+
+// TestFormatForAccept_JPEGXL verifies that the format auto chooses JPEG XL
+// when Accept names image/jxl, ahead of AVIF whatever their q, and AVIF when
+// Accept refuses JPEG XL with q=0.
+func TestFormatForAccept_JPEGXL(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name   string
+		accept string
+		want   imgcache.ImageFormat
+	}{
+		{"JPEG XL-capable browser",
+			"image/jxl,image/avif,image/webp,image/*,*/*;q=0.8", imgcache.FormatJXL},
+		{"JPEG XL only", jxlType, imgcache.FormatJXL},
+		{"JPEG XL with a lower q than AVIF", "image/avif,image/jxl;q=0.5",
+			imgcache.FormatJXL},
+		{"q=0 on JPEG XL", "image/jxl;q=0,image/avif,*/*", imgcache.FormatAVIF},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			got, err := formatForAccept(tt.accept)
+			if got != tt.want || err != nil {
+				t.Errorf("formatForAccept(%q) = %q, %v, want %q",
+					tt.accept, got, err, tt.want)
+			}
+		})
+	}
+}
+
+// TestFormatAuto_JPEGXL requests an auto URL on each image route with an
+// Accept header that names image/jxl, and checks that the answer is a JPEG XL
+// image.
+func TestFormatAuto_JPEGXL(t *testing.T) {
+	t.Parallel()
+
+	h, srv := newSignedHostServer(t, slog.New(slog.DiscardHandler))
+	signedURL, encryptedURL := autoPhotoURLs(t, h)
+
+	for _, target := range []string{signedURL, encryptedURL} {
+		rec := requestImage(t, srv, http.MethodGet, target,
+			"image/jxl,image/avif,image/webp,*/*;q=0.8")
+		gotType := rec.Header().Get("Content-Type")
+
+		if rec.Code != http.StatusOK || gotType != jxlType {
+			t.Errorf("%s: %d %s, want 200 %s; body %s",
+				target, rec.Code, gotType, jxlType, rec.Body)
+
+			continue
+		}
+
+		if got := vips.DetermineImageType(rec.Body.Bytes()); got != vips.ImageTypeJXL {
+			t.Errorf("%s: body is %s, want jxl", target, vips.ImageTypes[got])
+		}
+	}
+}

internal/httpfetcher/httpfetcher.go

@@ -45,6 +45,7 @@ const (
 	contentTypeGIF         = "image/gif"
 	contentTypeWebP        = "image/webp"
 	contentTypeAVIF        = "image/avif"
+	contentTypeJXL         = "image/jxl"
 	contentTypeSVG         = "image/svg+xml"
 	contentTypeOctetStream = "application/octet-stream"
 )
@@ -156,6 +157,7 @@ func DefaultConfig() *Config {
 			contentTypeGIF,
 			contentTypeWebP,
 			contentTypeAVIF,
+			contentTypeJXL,
 			contentTypeSVG,
 		},
 		AllowHTTP:             false,

internal/httpfetcher/jpegxl_internal_test.go

@@ -0,0 +1,20 @@
+package httpfetcher
+
+import "testing"
+
+// TestJPEGXLContentType verifies that the fetcher accepts an upstream answer
+// of type image/jxl by default, and that the mock fetcher serves a .jxl file
+// as image/jxl.
+func TestJPEGXLContentType(t *testing.T) {
+	t.Parallel()
+
+	const jxlType = "image/jxl"
+
+	if !New(DefaultConfig()).isAllowedContentType(jxlType) {
+		t.Errorf("isAllowedContentType(%q) = false, want true", jxlType)
+	}
+
+	if got := detectContentTypeFromPath("images/photo.jxl"); got != jxlType {
+		t.Errorf("detectContentTypeFromPath(photo.jxl) = %q, want %q", got, jxlType)
+	}
+}

internal/httpfetcher/mock.go

@@ -109,6 +109,8 @@ func detectContentTypeFromPath(path string) string {
 		return contentTypeWebP
 	case strings.HasSuffix(path, ".avif"):
 		return contentTypeAVIF
+	case strings.HasSuffix(path, ".jxl"):
+		return contentTypeJXL
 	case strings.HasSuffix(path, ".svg"):
 		return contentTypeSVG
 	default:

internal/imageprocessor/imageprocessor.go

@@ -65,6 +65,7 @@ const (
 	FormatPNG      Format = "png"
 	FormatWebP     Format = "webp"
 	FormatAVIF     Format = "avif"
+	FormatJXL      Format = "jxl"
 	FormatGIF      Format = "gif"
 )
 
@@ -305,6 +306,7 @@ const (
 	mimeGIF  = "image/gif"
 	mimeWebP = "image/webp"
 	mimeAVIF = "image/avif"
+	mimeJXL  = "image/jxl"
 )
 
 // SupportedInputFormats returns MIME types this processor can read.
@@ -315,6 +317,7 @@ func (p *ImageProcessor) SupportedInputFormats() []string {
 		mimeGIF,
 		mimeWebP,
 		mimeAVIF,
+		mimeJXL,
 	}
 }
 
@@ -326,6 +329,7 @@ func (p *ImageProcessor) SupportedOutputFormats() []Format {
 		FormatGIF,
 		FormatWebP,
 		FormatAVIF,
+		FormatJXL,
 	}
 }
 
@@ -342,6 +346,8 @@ func FormatToMIME(format Format) string {
 		return mimeGIF
 	case FormatAVIF:
 		return mimeAVIF
+	case FormatJXL:
+		return mimeJXL
 	case FormatOriginal:
 		return "application/octet-stream"
 	default:
@@ -411,9 +417,11 @@ func (p *ImageProcessor) detectFormat(img *vips.ImageRef) string {
 		return "webp"
 	case vips.ImageTypeAVIF, vips.ImageTypeHEIF:
 		return string(FormatAVIF)
+	case vips.ImageTypeJXL:
+		return string(FormatJXL)
 	case vips.ImageTypeUnknown, vips.ImageTypeMagick, vips.ImageTypePDF,
 		vips.ImageTypeSVG, vips.ImageTypeTIFF, vips.ImageTypeBMP,
-		vips.ImageTypeJP2K, vips.ImageTypeJXL:
+		vips.ImageTypeJP2K:
 		return "unknown"
 	default:
 		return "unknown"
@@ -485,6 +493,17 @@ func (p *ImageProcessor) encode(
 		quality = defaultQuality
 	}
 
+	// Stripping drops the ICC profile as well, and clients show an image
+	// with no profile as sRGB, so convert to sRGB first. "srgb" names
+	// libvips' built-in profile; govips' own sRGB path variable is set on
+	// first use but read without a lock, so concurrent requests race on it.
+	if img.HasICCProfile() {
+		err := img.TransformICCProfileWithFallback("srgb", "srgb")
+		if err != nil {
+			return nil, fmt.Errorf("failed to convert to sRGB: %w", err)
+		}
+	}
+
 	var params vips.ExportParams
 
 	switch format {
@@ -516,6 +535,9 @@ func (p *ImageProcessor) encode(
 			Quality: quality,
 		}
 
+	case FormatJXL:
+		return exportJXL(img, quality)
+
 	case FormatOriginal:
 		return nil, fmt.Errorf("%w: %s", ErrUnsupportedOutputFormat, format)
 
@@ -523,17 +545,6 @@ func (p *ImageProcessor) encode(
 		return nil, fmt.Errorf("%w: %s", ErrUnsupportedOutputFormat, format)
 	}
 
-	// Stripping drops the ICC profile as well, and clients show an image
-	// with no profile as sRGB, so convert to sRGB first. "srgb" names
-	// libvips' built-in profile; govips' own sRGB path variable is set on
-	// first use but read without a lock, so concurrent requests race on it.
-	if img.HasICCProfile() {
-		err := img.TransformICCProfileWithFallback("srgb", "srgb")
-		if err != nil {
-			return nil, fmt.Errorf("failed to convert to sRGB: %w", err)
-		}
-	}
-
 	// Drop EXIF, XMP, IPTC and the ICC profile. govips ignores this for
 	// GIF, which carries none of them.
 	params.StripMetadata = true
@@ -546,6 +557,78 @@ func (p *ImageProcessor) encode(
 	return output, nil
 }
 
+// jxlResolution is the resolution every JPEG XL image is saved with, in
+// pixels per millimetre as libvips counts it: 72 dpi, what libvips gives a
+// JPEG that names none.
+const jxlResolution = 72 / 25.4
+
+// exportJXL encodes img as JPEG XL at quality, with libvips' default effort
+// and without metadata. govips sends libvips a distance, the JPEG XL
+// encoder's own measure of quality, along with the quality, and libvips then
+// uses the distance alone, so the quality is also given as a distance.
+func exportJXL(img *vips.ImageRef, quality int) ([]byte, error) {
+	// libvips converts a CMYK image to sRGB before it saves WebP, AVIF or
+	// PNG, but cannot save one as JPEG XL. encode has already converted
+	// any image with an ICC profile to sRGB, so this is CMYK with none.
+	if img.Interpretation() == vips.InterpretationCMYK {
+		err := img.ToColorSpace(vips.InterpretationSRGB)
+		if err != nil {
+			return nil, fmt.Errorf("failed to convert CMYK to sRGB: %w", err)
+		}
+	}
+
+	// govips cannot make libvips strip metadata from JPEG XL, so it is
+	// removed from the image itself. RemoveMetadata removes EXIF, XMP and
+	// IPTC but keeps the ICC profile.
+	err := img.RemoveMetadata()
+	if err != nil {
+		return nil, err
+	}
+
+	err = img.RemoveICCProfile()
+	if err != nil {
+		return nil, err
+	}
+
+	// libvips 8.16 and later still write an EXIF block of their own, from
+	// the image's size, orientation and resolution, and fixed values. The
+	// image is upright, so its orientation is 1, but its resolution is still
+	// the source's.
+	toSave, err := img.CopyChangingResolution(jxlResolution, jxlResolution)
+	if err != nil {
+		return nil, err
+	}
+
+	defer toSave.Close()
+
+	params := vips.NewJxlExportParams()
+	params.Quality = quality
+	params.Distance = jxlDistance(quality)
+
+	output, _, err := toSave.ExportJxl(params)
+	if err != nil {
+		return nil, err
+	}
+
+	return output, nil
+}
+
+// jxlDistance turns a quality from 1 to 100 into the JPEG XL encoder's
+// distance, with the formula libvips and libjxl use for their own quality
+// setting, except that 100 stays lossy (distance 0.1) where libjxl makes it
+// lossless.
+//
+//nolint:mnd // the constants of that formula
+func jxlDistance(quality int) float64 {
+	q := float64(quality)
+
+	if quality >= 30 {
+		return 0.1 + (100-q)*0.09
+	}
+
+	return 53.0/3000.0*q*q - 23.0/20.0*q + 25.0
+}
+
 // formatFromString converts a format string to Format.
 func (p *ImageProcessor) formatFromString(format string) Format {
 	switch format {
@@ -559,6 +642,8 @@ func (p *ImageProcessor) formatFromString(format string) Format {
 		return FormatWebP
 	case string(FormatAVIF):
 		return FormatAVIF
+	case string(FormatJXL):
+		return FormatJXL
 	default:
 		return FormatJPEG
 	}

internal/imageprocessor/jpegxl_output_internal_test.go

@@ -0,0 +1,244 @@
+package imageprocessor
+
+import (
+	"bytes"
+	"io"
+	"math"
+	"os"
+	"testing"
+
+	"github.com/davidbyttow/govips/v2/vips"
+)
+
+// TestImageProcessor_EncodeJPEGXL converts a JPEG to a smaller JPEG XL and
+// checks the content type, and the format and size the output loads as.
+func TestImageProcessor_EncodeJPEGXL(t *testing.T) {
+	t.Parallel()
+
+	req := &Request{Size: Size{Width: 100, Height: 75}, Format: FormatJXL}
+
+	result, err := New(Params{}).Process(
+		t.Context(), bytes.NewReader(createTestJPEG(t, 200, 150)), req,
+	)
+	if err != nil {
+		t.Fatalf("Process() error = %v", err)
+	}
+
+	defer func() { _ = result.Content.Close() }()
+
+	if result.ContentType != "image/jxl" {
+		t.Errorf("ContentType = %q, want image/jxl", result.ContentType)
+	}
+
+	data, err := io.ReadAll(result.Content)
+	if err != nil {
+		t.Fatalf("failed to read result: %v", err)
+	}
+
+	output, err := vips.NewImageFromBuffer(data)
+	if err != nil {
+		t.Fatalf("failed to load the output: %v", err)
+	}
+
+	defer output.Close()
+
+	if output.Format() != vips.ImageTypeJXL {
+		t.Errorf("output format = %s, want jxl", vips.ImageTypes[output.Format()])
+	}
+
+	if output.Width() != 100 || output.Height() != 75 {
+		t.Errorf("output size = %dx%d, want 100x75", output.Width(), output.Height())
+	}
+}
+
+// TestImageProcessor_JPEGXLQuality verifies that the quality reaches the JPEG
+// XL encoder: the same image comes out smaller at quality 30 than at 90.
+func TestImageProcessor_JPEGXLQuality(t *testing.T) {
+	t.Parallel()
+
+	input := createTestJPEG(t, 400, 300)
+	outputBytes := make(map[int]int64)
+
+	for _, quality := range []int{30, 90} {
+		result, err := New(Params{}).Process(t.Context(),
+			bytes.NewReader(input), &Request{Format: FormatJXL, Quality: quality})
+		if err != nil {
+			t.Fatalf("Process() at quality %d error = %v", quality, err)
+		}
+
+		_ = result.Content.Close()
+		outputBytes[quality] = result.ContentLength
+	}
+
+	if outputBytes[30] >= outputBytes[90] {
+		t.Errorf("%d bytes at quality 30, %d at 90, want fewer at 30",
+			outputBytes[30], outputBytes[90])
+	}
+}
+
+// TestImageProcessor_JPEGXLDropsSourceEXIF verifies that none of the source's
+// EXIF reaches a JPEG XL output. libvips 8.16 and later write an EXIF block of
+// their own into JPEG XL (orientation, resolution, size, colour space and
+// fixed defaults), and govips cannot ask them to leave it out, so the test
+// looks for the source's fields rather than for no EXIF at all.
+func TestImageProcessor_JPEGXLDropsSourceEXIF(t *testing.T) {
+	t.Parallel()
+
+	input, err := os.ReadFile("testdata/gps-exif.jpg")
+	if err != nil {
+		t.Fatalf("failed to read test JPEG: %v", err)
+	}
+
+	exif := processAndDecode(t, input, &Request{Format: FormatJXL}).GetExif()
+
+	for _, field := range []string{
+		"exif-ifd0-Make", "exif-ifd0-Model", "exif-ifd2-BodySerialNumber",
+		"exif-ifd2-DateTimeOriginal", "exif-ifd3-GPSLatitude",
+		"exif-ifd3-GPSLongitude",
+	} {
+		if value, found := exif[field]; found {
+			t.Errorf("output has %s: %s", field, value)
+		}
+	}
+}
+
+// TestImageProcessor_JPEGXLDropsSourceResolution verifies that the source's
+// resolution does not reach the EXIF block libvips 8.16 and later write into
+// JPEG XL. A JPEG XL image holds its resolution in that block alone, so the
+// resolution the output loads with is the block's.
+func TestImageProcessor_JPEGXLDropsSourceResolution(t *testing.T) {
+	t.Parallel()
+
+	// dpi-300.jpg is a flat 8x8 grey image with a resolution of 300 dpi.
+	input, err := os.ReadFile("testdata/dpi-300.jpg")
+	if err != nil {
+		t.Fatalf("failed to read test JPEG: %v", err)
+	}
+
+	output := processAndDecode(t, input, &Request{Format: FormatJXL})
+
+	// libvips gives the resolution in pixels per millimetre.
+	xDPI := math.Round(output.ResX() * 25.4)
+	yDPI := math.Round(output.ResY() * 25.4)
+
+	if xDPI == 300 || yDPI == 300 {
+		t.Errorf("output resolution = %vx%v dpi, the source's", xDPI, yDPI)
+	}
+}
+
+// TestImageProcessor_JPEGXLAppliesEXIFOrientation verifies that a JPEG XL
+// output is turned upright, as TestImageProcessor_AppliesEXIFOrientation does
+// for PNG.
+func TestImageProcessor_JPEGXLAppliesEXIFOrientation(t *testing.T) {
+	t.Parallel()
+
+	// orientation-6.jpg is stored 16x8, red on the left and blue on the
+	// right, with EXIF orientation 6 (turn 90 degrees clockwise to view).
+	// Upright it is 8x16, red on top and blue below.
+	input, err := os.ReadFile("testdata/orientation-6.jpg")
+	if err != nil {
+		t.Fatalf("failed to read test JPEG: %v", err)
+	}
+
+	output := processAndDecode(t, input, &Request{Format: FormatJXL})
+
+	if output.Width() != 8 || output.Height() != 16 {
+		t.Fatalf("output is %dx%d, want 8x16", output.Width(), output.Height())
+	}
+
+	top, err := output.GetPoint(4, 0)
+	if err != nil {
+		t.Fatalf("GetPoint() error = %v", err)
+	}
+
+	bottom, err := output.GetPoint(4, 15)
+	if err != nil {
+		t.Fatalf("GetPoint() error = %v", err)
+	}
+
+	if top[0] <= top[2] || bottom[2] <= bottom[0] {
+		t.Errorf("top pixel = %v, bottom pixel = %v, want red above blue",
+			top, bottom)
+	}
+}
+
+// TestImageProcessor_JPEGXLConvertsWideGamutToSRGB verifies that a JPEG XL
+// output is converted to sRGB, as TestImageProcessor_ConvertsWideGamutToSRGB
+// does for PNG. It does not check for an ICC profile, as libvips reports one
+// for every JPEG XL image it loads.
+func TestImageProcessor_JPEGXLConvertsWideGamutToSRGB(t *testing.T) {
+	t.Parallel()
+
+	// display-p3.jpg is a flat 8x8 image with the Display P3 profile
+	// embedded, filled with Display P3 (234, 51, 35), which is sRGB red.
+	input, err := os.ReadFile("testdata/display-p3.jpg")
+	if err != nil {
+		t.Fatalf("failed to read test JPEG: %v", err)
+	}
+
+	output := processAndDecode(t, input, &Request{Format: FormatJXL})
+
+	pixel, err := output.GetPoint(4, 4)
+	if err != nil {
+		t.Fatalf("GetPoint() error = %v", err)
+	}
+
+	want := []float64{255, 0, 0}
+	for i := range want {
+		if math.Abs(pixel[i]-want[i]) > 5 {
+			t.Fatalf("pixel = %v, want within 5 of %v", pixel, want)
+		}
+	}
+}
+
+// TestImageProcessor_JPEGXLFromCMYK verifies that a CMYK JPEG with no ICC
+// profile can be served as JPEG XL, in sRGB.
+func TestImageProcessor_JPEGXLFromCMYK(t *testing.T) {
+	t.Parallel()
+
+	// cmyk.jpg is a flat 8x8 CMYK image with no ICC profile, filled with
+	// full cyan and no magenta, yellow or black.
+	input, err := os.ReadFile("testdata/cmyk.jpg")
+	if err != nil {
+		t.Fatalf("failed to read test JPEG: %v", err)
+	}
+
+	output := processAndDecode(t, input, &Request{Format: FormatJXL})
+
+	if output.Bands() != 3 {
+		t.Fatalf("output has %d bands, want 3", output.Bands())
+	}
+
+	pixel, err := output.GetPoint(4, 4)
+	if err != nil {
+		t.Fatalf("GetPoint() error = %v", err)
+	}
+
+	// Cyan in sRGB: little red, much green and blue.
+	if pixel[0] > 50 || pixel[1] < 100 || pixel[2] < 200 {
+		t.Errorf("pixel = %v, want cyan", pixel)
+	}
+}
+
+// TestJXLDistance verifies the JPEG XL distance for a few qualities: 90 is
+// distance 1, the encoder's own default, and 100 stays lossy.
+func TestJXLDistance(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		quality int
+		want    float64
+	}{
+		{quality: 100, want: 0.1},
+		{quality: 90, want: 1},
+		{quality: 30, want: 6.4},
+		{quality: 20, want: 9.0667},
+	}
+
+	for _, tt := range tests {
+		got := jxlDistance(tt.quality)
+		if math.Abs(got-tt.want) > 0.0001 {
+			t.Errorf("jxlDistance(%d) = %v, want %v", tt.quality, got, tt.want)
+		}
+	}
+}

internal/imgcache/imgcache.go

@@ -21,11 +21,12 @@ const (
 	FormatPNG      ImageFormat = "png"
 	FormatWebP     ImageFormat = "webp"
 	FormatAVIF     ImageFormat = "avif"
+	FormatJXL      ImageFormat = "jxl"
 	FormatGIF      ImageFormat = "gif"
 
-	// FormatAuto stands for AVIF, WebP or JPEG, chosen for each request
-	// from its Accept header once the URL's signature or token has been
-	// checked; it is never processed or cached as itself.
+	// FormatAuto stands for JPEG XL, AVIF, WebP or JPEG, chosen for each
+	// request from its Accept header once the URL's signature or token has
+	// been checked; it is never processed or cached as itself.
 	FormatAuto ImageFormat = "auto"
 )
 

internal/imgcache/urlparser.go

@@ -275,6 +275,8 @@ func parseFormat(s string) (ImageFormat, error) {
 		return FormatWebP, nil
 	case "avif":
 		return FormatAVIF, nil
+	case "jxl":
+		return FormatJXL, nil
 	case "gif":
 		return FormatGIF, nil
 	case "auto":

internal/magic/jpegxl_internal_test.go

@@ -0,0 +1,58 @@
+package magic
+
+import "testing"
+
+// testMIMEJXL is the MIME type of JPEG XL.
+const testMIMEJXL = "image/jxl"
+
+// TestDetectFormatJPEGXL verifies that both JPEG XL signatures, that of a
+// bare codestream and that of the container, are detected as image/jxl.
+func TestDetectFormatJPEGXL(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		data []byte
+	}{
+		{"codestream", pad(0xFF, 0x0A)},
+		{"container", pad(
+			0x00, 0x00, 0x00, 0x0C, 0x4A, 0x58, 0x4C, 0x20, 0x0D, 0x0A, 0x87, 0x0A,
+		)},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			got, err := DetectFormat(tt.data)
+			if err != nil || got != MIMETypeJXL {
+				t.Errorf("DetectFormat() = %q, %v, want %q", got, err, testMIMEJXL)
+			}
+
+			err = ValidateMagicBytes(tt.data, testMIMEJXL)
+			if err != nil {
+				t.Errorf("ValidateMagicBytes(%q) error = %v", testMIMEJXL, err)
+			}
+		})
+	}
+}
+
+// TestJPEGXLMIMEType verifies that image/jxl is a supported input type and
+// maps to and from the format jxl.
+func TestJPEGXLMIMEType(t *testing.T) {
+	t.Parallel()
+
+	if !IsSupportedMIMEType(testMIMEJXL) {
+		t.Errorf("IsSupportedMIMEType(%q) = false", testMIMEJXL)
+	}
+
+	format, ok := MIMEToImageFormat(testMIMEJXL)
+	if format != FormatJXL || !ok {
+		t.Errorf("MIMEToImageFormat(%q) = %q, %v, want %q, true",
+			testMIMEJXL, format, ok, FormatJXL)
+	}
+
+	if got := ImageFormatToMIME(FormatJXL); got != testMIMEJXL {
+		t.Errorf("ImageFormatToMIME(%q) = %q, want %q", FormatJXL, got, testMIMEJXL)
+	}
+}

internal/magic/magic.go

@@ -26,6 +26,7 @@ const (
 	MIMETypeWebP = MIMEType("image/webp")
 	MIMETypeGIF  = MIMEType("image/gif")
 	MIMETypeAVIF = MIMEType("image/avif")
+	MIMETypeJXL  = MIMEType("image/jxl")
 	MIMETypeSVG  = MIMEType("image/svg+xml")
 )
 
@@ -40,6 +41,7 @@ const (
 	FormatPNG      ImageFormat = "png"
 	FormatWebP     ImageFormat = "webp"
 	FormatAVIF     ImageFormat = "avif"
+	FormatJXL      ImageFormat = "jxl"
 	FormatGIF      ImageFormat = "gif"
 )
 
@@ -62,6 +64,11 @@ var (
 	// AVIF uses the ftyp box with brand "avif" or "avis"
 	// Format: size(4 bytes) + "ftyp" + brand(4 bytes)
 	magicFtyp = []byte{0x66, 0x74, 0x79, 0x70} // "ftyp"
+	// JPEG XL is a bare codestream or a codestream in a container
+	magicJXLCodestream = []byte{0xFF, 0x0A}
+	magicJXLContainer  = []byte{
+		0x00, 0x00, 0x00, 0x0C, 0x4A, 0x58, 0x4C, 0x20, 0x0D, 0x0A, 0x87, 0x0A,
+	}
 )
 
 // WebP identifier appears at offset 8 after RIFF header.
@@ -115,6 +122,12 @@ func DetectFormat(data []byte) (MIMEType, error) {
 		}
 	}
 
+	// Check JPEG XL (FF0A, or the 12-byte container signature)
+	if bytes.HasPrefix(data, magicJXLCodestream) ||
+		bytes.HasPrefix(data, magicJXLContainer) {
+		return MIMETypeJXL, nil
+	}
+
 	// Check SVG - look for XML declaration or SVG tag
 	if detectSVG(data) {
 		return MIMETypeSVG, nil
@@ -181,7 +194,8 @@ func normalizeMIMEType(mimeType string) string {
 func IsSupportedMIMEType(mimeType string) bool {
 	normalized := normalizeMIMEType(mimeType)
 	switch MIMEType(normalized) {
-	case MIMETypeJPEG, MIMETypePNG, MIMETypeWebP, MIMETypeGIF, MIMETypeAVIF, MIMETypeSVG:
+	case MIMETypeJPEG, MIMETypePNG, MIMETypeWebP, MIMETypeGIF, MIMETypeAVIF,
+		MIMETypeJXL, MIMETypeSVG:
 		return true
 	default:
 		return false
@@ -226,6 +240,8 @@ func MIMEToImageFormat(mimeType string) (ImageFormat, bool) {
 		return FormatGIF, true
 	case MIMETypeAVIF:
 		return FormatAVIF, true
+	case MIMETypeJXL:
+		return FormatJXL, true
 	case MIMETypeSVG:
 		// SVG has no corresponding output format.
 		return "", false
@@ -247,6 +263,8 @@ func ImageFormatToMIME(format ImageFormat) string {
 		return string(MIMETypeGIF)
 	case FormatAVIF:
 		return string(MIMETypeAVIF)
+	case FormatJXL:
+		return string(MIMETypeJXL)
 	case FormatOriginal:
 		// Original format passes content through unchanged.
 		return mimeOctetStream

internal/server/jpegxl_internal_test.go

@@ -0,0 +1,72 @@
+package server
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+
+	"github.com/davidbyttow/govips/v2/vips"
+)
+
+// TestImageProxyFlowJPEGXL requests the JPEG XL testdata/red.jxl, 64x48 and
+// made with libvips, through pixa's router, upstream fetcher, image processor
+// and disk cache: resized as PNG, resized as JPEG XL, and at its own size and
+// format, which is JPEG XL. The second request for each URL is a cache hit.
+func TestImageProxyFlowJPEGXL(t *testing.T) {
+	t.Parallel()
+
+	source, err := os.ReadFile("testdata/red.jxl")
+	if err != nil {
+		t.Fatalf("reading the test image: %v", err)
+	}
+
+	upstream := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, _ *http.Request) {
+			w.Header().Set("Content-Type", "image/jxl")
+			_, _ = w.Write(source)
+		}))
+	t.Cleanup(upstream.Close)
+
+	s, _, _ := startImageProxy(t, upstream)
+
+	tests := []struct {
+		sizeFormat    string // the <size>.<format> part of the image URL
+		contentType   string
+		imageType     vips.ImageType
+		width, height int
+	}{
+		{"32x24.png", "image/png", vips.ImageTypePNG, 32, 24},
+		{"32x24.jxl", "image/jxl", vips.ImageTypeJXL, 32, 24},
+		{"orig.orig", "image/jxl", vips.ImageTypeJXL, 64, 48},
+	}
+
+	for _, tt := range tests {
+		target := "/v1/image/" + upstreamHost + "/red.jxl/" + tt.sizeFormat
+
+		for _, wantCache := range []string{"MISS", "HIT"} {
+			rec := getImage(t, s, target)
+			gotType := rec.Header().Get("Content-Type")
+			gotCache := rec.Header().Get("X-Pixa-Cache")
+
+			if gotType != tt.contentType || gotCache != wantCache {
+				t.Errorf("%s: %s, X-Pixa-Cache %s, want %s, %s",
+					target, gotType, gotCache, tt.contentType, wantCache)
+			}
+
+			img, err := vips.NewImageFromBuffer(rec.Body.Bytes())
+			if err != nil {
+				t.Fatalf("%s: loading the image: %v", target, err)
+			}
+
+			if img.Format() != tt.imageType ||
+				img.Width() != tt.width || img.Height() != tt.height {
+				t.Errorf("%s: %s %dx%d, want %s %dx%d", target,
+					vips.ImageTypes[img.Format()], img.Width(), img.Height(),
+					vips.ImageTypes[tt.imageType], tt.width, tt.height)
+			}
+
+			img.Close()
+		}
+	}
+}

internal/templates/generator.html

@@ -95,11 +95,12 @@
                     </label>
                     <select id="format" name="format">
                         <option value="orig" {{if eq .FormFormat "orig"}}selected{{end}}>Original</option>
-                        <option value="auto" {{if eq .FormFormat "auto"}}selected{{end}}>Auto (AVIF, WebP or JPEG)</option>
+                        <option value="auto" {{if eq .FormFormat "auto"}}selected{{end}}>Auto (JPEG XL, AVIF, WebP or JPEG)</option>
                         <option value="jpeg" {{if eq .FormFormat "jpeg"}}selected{{end}}>JPEG</option>
                         <option value="png" {{if eq .FormFormat "png"}}selected{{end}}>PNG</option>
                         <option value="webp" {{if eq .FormFormat "webp"}}selected{{end}}>WebP</option>
                         <option value="avif" {{if eq .FormFormat "avif"}}selected{{end}}>AVIF</option>
+                        <option value="jxl" {{if eq .FormFormat "jxl"}}selected{{end}}>JPEG XL</option>
                         <option value="gif" {{if eq .FormFormat "gif"}}selected{{end}}>GIF</option>
                     </select>
                 </div>