Save PNG compressed, WebP at effort 4 and AVIF at effort 1 (closes #232)

Each output format now has its own govips export with its settings
named, in place of govips' generic Export, which sent libvips a zero for
some settings it was not given: PNG had no compression and WebP effort
0. PNG now gets libvips' default compression, 6, and WebP its default
effort, 4. GIF and JPEG output is unchanged.

AVIF was at libvips' default effort, 4, which takes minutes for an
8192x8192 image with one libvips thread, far past the default
downstream_timeout. Effort 1, the lowest govips can set, takes about 51
seconds for an image of random pixels, the worst case, and WebP at 4
about 43. A 16-bit source gets 8 bits per sample, not libvips' 12, which
take over four times as long.

Model: opus-5-5

README.md

@@ -175,20 +175,21 @@ path under `/v1/` answers 200, in maintenance mode too.
   with the page naming a field that is not valid; 500 when the URL cannot be
   made.
 - `GET /logout` — end the login session. Needs: nothing. Answers: 303 to `/`.
-- `GET` or `HEAD` `/v1/image/<host>/<path>/<size>.<format>` — an image, fetched,
-  resized and converted (below). Needs: a signature, unless the host is
-  allowlisted (see Source Hosts). Answers: 200; 304 when `If-None-Match` matches
-  the image's `ETag`; 400 for a URL or parameter that is not valid, or for the
-  format `auto` an `Accept` header that is not valid; 406 for the format `auto`
-  when `Accept` allows none of the formats it chooses from; 401 for a missing or
-  wrong signature, a missing `exp` or an `exp` in the past; 403 when the
-  request's `Referer` names a host in `referer_blocklist`, checked before the
-  signature, the cache and the upstream fetch; 403 when the upstream host, or a
-  host it redirects to, is `localhost`, ends in `.localhost` or `.local`, or has
-  an address in a blocked network (see `blocked_networks`); 502 when the
-  upstream answered with an error status, and for 5 minutes after that for the
-  same source URL; 503 when pixa is busy or in maintenance mode; 500 for any
-  other failure.
+- `GET` or `HEAD` `/v1/image/<host>/<path>/<size>.<format>`, or
+  `/v1/image/<host>/<path>/<size>` with no format — an image, fetched, resized
+  and converted (below). Needs: a signature, unless the host is allowlisted (see
+  Source Hosts). Answers: 200; 304 when `If-None-Match` matches the image's
+  `ETag`; 400 for a URL or parameter that is not valid, or for the format `auto`
+  an `Accept` header that is not valid; 406 for the format `auto` when `Accept`
+  allows none of the formats it chooses from; 401 for a missing or wrong
+  signature, a missing `exp` or an `exp` in the past; 403 when the request's
+  `Referer` names a host in `referer_blocklist`, checked before the signature,
+  the cache and the upstream fetch; 403 when the upstream host, or a host it
+  redirects to, is `localhost`, ends in `.localhost` or `.local`, or has an
+  address in a blocked network (see `blocked_networks`); 502 when the upstream
+  answered with an error status, and for 5 minutes after that for the same
+  source URL; 503 when pixa is busy or in maintenance mode; 500 for any other
+  failure.
 - `GET` or `HEAD` `/v1/e/<token>/<name>` — an image through an encrypted URL
   (see Encrypted URLs). Needs: nothing but the URL. Answers: 200; 304 when
   `If-None-Match` matches the image's `ETag`; 400 for a token that does not

TODO.md

@@ -30,6 +30,21 @@ P2: security: per-IP rate limiting on the image routes
 
 # Completed Steps
 
+- 2026-10-08 every output format is saved with settings pixa sets on purpose
+  (closes #232): each format has its own govips export, as JPEG XL does, in
+  place of govips' generic `Export`, which sent libvips a zero for some settings
+  it was not given. PNG gets libvips' default compression, 6, where it had none,
+  and WebP libvips' default effort, 4, where it had 0. GIF was already at
+  libvips' default effort, 7, and JPEG output is unchanged. AVIF is saved at
+  effort 1, the lowest govips can set, where it had libvips' default, 4. With
+  one libvips thread, an 8192x8192 image of random pixels, the worst case, takes
+  about 51 seconds as AVIF at effort 1 and 43 as WebP at effort 4, against the
+  default `downstream_timeout` of 60 seconds. On an image of milder noise, which
+  AVIF at effort 1 saves in about 12 seconds, effort 4 takes minutes. AVIF is
+  also saved with 8 bits per sample from a 16-bit source, which libvips would
+  save with 12: a 16-bit 8192x8192 image of milder noise takes about 54 seconds
+  at effort 1 with 12 bits, nearly all of the default `downstream_timeout`, and
+  about 12 with 8.
 - 2026-10-08 JPEG XL is the default output (closes #222): a `/v1/image/` URL
   whose last segment is a size with no format, such as `800x600` or `orig`, is
   served as JPEG XL and signed as `jxl`, so it has the signature of the same URL

internal/handlers/image.go

@@ -18,7 +18,8 @@ import (
 )
 
 // HandleImage handles the main image proxy route:
-// /v1/image/<host>/<path>/<width>x<height>.<format>
+// /v1/image/<host>/<path>/<width>x<height>.<format>, or with no format
+// /v1/image/<host>/<path>/<width>x<height>
 func (s *Handlers) HandleImage() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		if s.refuseBlockedReferer(w, r) {

internal/imageprocessor/encoder_settings_internal_test.go

@@ -0,0 +1,145 @@
+package imageprocessor
+
+import (
+	"bytes"
+	"image"
+	"image/color"
+	"image/png"
+	"testing"
+
+	"github.com/davidbyttow/govips/v2/vips"
+)
+
+// processedSize runs input through Process and returns the output's size in
+// bytes.
+func processedSize(t *testing.T, input []byte, req *Request) int64 {
+	t.Helper()
+
+	result, err := New(Params{}).Process(t.Context(), bytes.NewReader(input), req)
+	if err != nil {
+		t.Fatalf("Process() error = %v", err)
+	}
+
+	_ = result.Content.Close()
+
+	return result.ContentLength
+}
+
+// encodePNG encodes img as PNG with Go's encoder.
+func encodePNG(t *testing.T, img image.Image) []byte {
+	t.Helper()
+
+	var buf bytes.Buffer
+
+	err := png.Encode(&buf, img)
+	if err != nil {
+		t.Fatalf("failed to encode test PNG: %v", err)
+	}
+
+	return buf.Bytes()
+}
+
+// decode decodes input with vips, as Process does.
+func decode(t *testing.T, input []byte) *vips.ImageRef {
+	t.Helper()
+
+	img, err := vips.NewImageFromBuffer(input)
+	if err != nil {
+		t.Fatalf("failed to decode input: %v", err)
+	}
+
+	t.Cleanup(img.Close)
+
+	return img
+}
+
+// TestImageProcessor_PNGIsCompressed verifies that a PNG output is
+// compressed: a flat 200x150 image, 90,000 bytes of raw pixels, comes out at
+// a small fraction of that.
+func TestImageProcessor_PNGIsCompressed(t *testing.T) {
+	t.Parallel()
+
+	const width, height = 200, 150
+
+	flat := image.NewRGBA(image.Rect(0, 0, width, height))
+	for y := range height {
+		for x := range width {
+			flat.Set(x, y, color.RGBA{R: 40, G: 120, B: 200, A: 255})
+		}
+	}
+
+	size := processedSize(t, encodePNG(t, flat), &Request{Format: FormatPNG})
+
+	const rawBytes = width * height * 3
+	if size > rawBytes/10 {
+		t.Errorf("PNG output is %d bytes, want under a tenth of its %d raw",
+			size, rawBytes)
+	}
+}
+
+// TestImageProcessor_WebPAtDefaultEffort verifies that WebP is saved at
+// libvips' default effort, 4: the output is the size of the same image saved
+// at that effort.
+func TestImageProcessor_WebPAtDefaultEffort(t *testing.T) {
+	t.Parallel()
+
+	input := createTestJPEG(t, 200, 150)
+
+	size := processedSize(t, input, &Request{Format: FormatWebP, Quality: 85})
+
+	want, _, err := decode(t, input).ExportWebp(&vips.WebpExportParams{
+		StripMetadata:   true,
+		Quality:         85,
+		ReductionEffort: 4,
+	})
+	if err != nil {
+		t.Fatalf("ExportWebp() error = %v", err)
+	}
+
+	if size != int64(len(want)) {
+		t.Errorf("WebP output is %d bytes, want %d, the size at effort 4",
+			size, len(want))
+	}
+}
+
+// TestImageProcessor_AVIFAtEffort1 verifies that AVIF is saved at effort 1
+// with 8 bits per sample: the output is the size of the same image saved
+// with those settings. The source is 16-bit, which libvips saves with 12
+// bits when it is not given a bit depth, and 640x480: on a small image,
+// such as 64x48, efforts 1 and 2 give the same output.
+func TestImageProcessor_AVIFAtEffort1(t *testing.T) {
+	t.Parallel()
+
+	const width, height = 640, 480
+
+	source := image.NewRGBA64(image.Rect(0, 0, width, height))
+	for y := range height {
+		for x := range width {
+			source.Set(x, y, color.RGBA64{
+				R: uint16((x * 65535 / width) & 0xffff),
+				G: uint16((y * 65535 / height) & 0xffff),
+				B: 32768,
+				A: 65535,
+			})
+		}
+	}
+
+	input := encodePNG(t, source)
+
+	size := processedSize(t, input, &Request{Format: FormatAVIF, Quality: 85})
+
+	want, _, err := decode(t, input).ExportAvif(&vips.AvifExportParams{
+		StripMetadata: true,
+		Quality:       85,
+		Effort:        1,
+		Bitdepth:      8,
+	})
+	if err != nil {
+		t.Fatalf("ExportAvif() error = %v", err)
+	}
+
+	if size != int64(len(want)) {
+		t.Errorf("AVIF output is %d bytes, want %d, the size at effort 1 "+
+			"and 8 bits", size, len(want))
+	}
+}

internal/imageprocessor/imageprocessor.go

@@ -504,36 +504,21 @@ func (p *ImageProcessor) encode(
 		}
 	}
 
-	var params vips.ExportParams
-
 	switch format {
 	case FormatJPEG:
-		params = vips.ExportParams{
-			Format:  vips.ImageTypeJPEG,
-			Quality: quality,
-		}
+		return exportJPEG(img, quality)
 
 	case FormatPNG:
-		params = vips.ExportParams{
-			Format: vips.ImageTypePNG,
-		}
+		return exportPNG(img)
 
 	case FormatGIF:
-		params = vips.ExportParams{
-			Format: vips.ImageTypeGIF,
-		}
+		return exportGIF(img)
 
 	case FormatWebP:
-		params = vips.ExportParams{
-			Format:  vips.ImageTypeWEBP,
-			Quality: quality,
-		}
+		return exportWebP(img, quality)
 
 	case FormatAVIF:
-		params = vips.ExportParams{
-			Format:  vips.ImageTypeAVIF,
-			Quality: quality,
-		}
+		return exportAVIF(img, quality)
 
 	case FormatJXL:
 		return exportJXL(img, quality)
@@ -544,17 +529,90 @@ func (p *ImageProcessor) encode(
 	default:
 		return nil, fmt.Errorf("%w: %s", ErrUnsupportedOutputFormat, format)
 	}
-
-	// Drop EXIF, XMP, IPTC and the ICC profile. govips ignores this for
-	// GIF, which carries none of them.
-	params.StripMetadata = true
-
-	output, _, err := img.Export(&params)
-	if err != nil {
-		return nil, err
 }
 
-	return output, nil
+// govips sends libvips Go's zero value for some settings an export leaves
+// out, such as no compression at all for PNG, so each export below sets
+// every setting whose zero value is not what pixa wants. Stripping metadata
+// drops EXIF, XMP, IPTC and the ICC profile.
+
+// exportJPEG encodes img as JPEG at quality, without metadata. The settings
+// it leaves out are at libvips' defaults.
+func exportJPEG(img *vips.ImageRef, quality int) ([]byte, error) {
+	output, _, err := img.ExportJpeg(&vips.JpegExportParams{
+		StripMetadata: true,
+		Quality:       quality,
+	})
+
+	return output, err
+}
+
+// pngCompression is libvips' default PNG compression, from 0 (none) to 9.
+const pngCompression = 6
+
+// exportPNG encodes img as PNG at libvips' default compression and row
+// filter, without metadata.
+func exportPNG(img *vips.ImageRef) ([]byte, error) {
+	output, _, err := img.ExportPng(&vips.PngExportParams{
+		StripMetadata: true,
+		Compression:   pngCompression,
+		Filter:        vips.PngFilterNone,
+	})
+
+	return output, err
+}
+
+// gifEffort is libvips' default GIF effort, from 1 to 10.
+const gifEffort = 7
+
+// exportGIF encodes img as GIF at libvips' default effort. govips cannot
+// have libvips strip metadata from GIF, which carries none.
+func exportGIF(img *vips.ImageRef) ([]byte, error) {
+	output, _, err := img.ExportGIF(&vips.GifExportParams{Effort: gifEffort})
+
+	return output, err
+}
+
+// webpEffort is libvips' default WebP effort, from 0 (fastest) to 6.
+const webpEffort = 4
+
+// exportWebP encodes img as lossy WebP at quality and libvips' default
+// effort, without metadata.
+func exportWebP(img *vips.ImageRef, quality int) ([]byte, error) {
+	output, _, err := img.ExportWebp(&vips.WebpExportParams{
+		StripMetadata:   true,
+		Quality:         quality,
+		ReductionEffort: webpEffort,
+	})
+
+	return output, err
+}
+
+// avifEffort is the AVIF effort, from 0 (fastest) to 9; 1 is the lowest
+// govips can set. With one thread, as pixad runs libvips, 1 takes about 51
+// seconds to save an 8192x8192 image of random pixels, the worst case,
+// against the default downstream_timeout of 60 seconds. On an image of
+// milder noise, which 1 saves in about 12 seconds, 2 takes nearly a minute
+// and libvips' default, 4, takes minutes.
+const avifEffort = 1
+
+// avifBitdepth is the AVIF bit depth, 8 bits per sample for every image.
+// libvips would save a 16-bit image with 12, but at avifEffort that takes
+// about 54 seconds for a 16-bit 8192x8192 image of milder noise, nearly all
+// of the default downstream_timeout, and about 12 seconds with 8.
+const avifBitdepth = 8
+
+// exportAVIF encodes img as lossy AVIF at quality, avifEffort and
+// avifBitdepth, without metadata.
+func exportAVIF(img *vips.ImageRef, quality int) ([]byte, error) {
+	output, _, err := img.ExportAvif(&vips.AvifExportParams{
+		StripMetadata: true,
+		Quality:       quality,
+		Effort:        avifEffort,
+		Bitdepth:      avifBitdepth,
+	})
+
+	return output, err
 }
 
 // jxlResolution is the resolution every JPEG XL image is saved with, in

internal/imgcache/service.go

@@ -100,8 +100,8 @@ func NewService(cfg *ServiceConfig) (*Service, error) {
 		allowHTTP = cfg.FetcherConfig.AllowHTTP
 	}
 
-	// JPEG XL is to become the default output format, so pixad does not
-	// start without it.
+	// JPEG XL is the default output format, so pixad does not start
+	// without it.
 	err := imageprocessor.CheckJPEGXLSupport()
 	if err != nil {
 		return nil, err

internal/imgcache/urlparser.go

@@ -75,7 +75,8 @@ func ParseImagePath(path string) (*ParsedURL, error) {
 	return parseImageComponents(path)
 }
 
-// ParseImageURL parses a full URL path like /v1/image/<host>/<path>/<size>.<format>
+// ParseImageURL parses a full URL path like /v1/image/<host>/<path>/<size>.<format>,
+// or /v1/image/<host>/<path>/<size> for JPEG XL
 // Use ParseImagePath instead when working with chi's wildcard capture.
 func ParseImageURL(urlPath string) (*ParsedURL, error) {
 	// Remove the /v1/image/ prefix
@@ -92,7 +93,8 @@ func ParseImageURL(urlPath string) (*ParsedURL, error) {
 	return parseImageComponents(remainder)
 }
 
-// parseImageComponents parses <host>/<path>/<size>.<format> structure.
+// parseImageComponents parses <host>/<path>/<size>.<format>, or
+// <host>/<path>/<size> for JPEG XL.
 func parseImageComponents(remainder string) (*ParsedURL, error) {
 	// Check for path traversal before any other processing
 	err := checkPathTraversal(remainder)
@@ -100,7 +102,7 @@ func parseImageComponents(remainder string) (*ParsedURL, error) {
 		return nil, err
 	}
 
-	// Find the last path segment which contains size.format
+	// Find the last path segment, which holds "size" or "size.format"
 	lastSlash := strings.LastIndex(remainder, "/")
 	if lastSlash == -1 {
 		return nil, ErrMissingSize
@@ -228,11 +230,11 @@ func parseSizeFormat(s string) (Size, ImageFormat, error) {
 	)
 
 	if matches[4] == "orig" {
-		// "orig.format" pattern
+		// "orig" or "orig.format" pattern
 		size = Size{Width: 0, Height: 0}
 		formatStr = matches[5]
 	} else {
-		// "WxH.format" pattern
+		// "WxH" or "WxH.format" pattern
 		width, err := strconv.Atoi(matches[1])
 		if err != nil {
 			return Size{}, "", ErrInvalidSize

internal/server/routes.go

@@ -89,7 +89,8 @@ func (s *Server) SetupRoutes() {
 			r.Use(s.refuseDuringMaintenance)
 
 			// Main image proxy route
-			// /v1/image/<host>/<path>/<width>x<height>.<format>
+			// /v1/image/<host>/<path>/<width>x<height>.<format>, or with no
+			// format /v1/image/<host>/<path>/<width>x<height>
 			r.Get("/image/*", s.h.HandleImage())
 			r.Head("/image/*", s.h.HandleImage())