Thumbs: Enhance embedding of ICC profiles based on InteropIndex #5178

Signed-off-by: Michael Mayer <michael@photoprism.app>

AGENTS.md

@@ -1,6 +1,6 @@
 # PhotoPrism® Repository Guidelines
 
-**Last Updated:** November 21, 2025
+**Last Updated:** November 23, 2025
 
 ## Purpose
 
@@ -212,6 +212,7 @@ Note: Across our public documentation, official images, and in production, the c
 ## Code Style & Lint
 
 - Go: run `make fmt-go swag-fmt` to reformat the backend code + Swagger annotations (see `Makefile` for additional targets)
+  - Run `make lint-go` (golangci-lint) after Go changes; prefer `golangci-lint run ./internal/<pkg>/...` for focused edits.
   - Doc comments for packages and exported identifiers must be complete sentences that begin with the name of the thing being described and end with a period.
   - All newly added functions, including unexported helpers, must have a concise doc comment that explains their behavior.
   - For short examples inside comments, indent code rather than using backticks; godoc treats indented blocks as preformatted.

assets/profiles/icc/NOTICE

@@ -1,54 +1,122 @@
+================================================================================
+================================================================================
 
-Files: compatibleWithAdobeRGB1998.icc
-Source: Debian icc-profiles-free
- https://salsa.debian.org/debian/icc-profiles-free/-/tree/a7a3c11b8a6d3bc2937447183b87dc89de9d2388/icc-profiles-openicc/default_profiles/base
-Copyright:  Kai-Uwe Behrmann <www.behrmann.name>
-            Marti Maria <www.littlecms.com>
-            Photogamut <www.photogamut.org>
-            Graeme Gill <www.argyllcms.com>
-            ColorSolutions <www.basICColor.com>
-License: Zlib
+                      Third-Party ICC Profiles for PhotoPrism
+
+--------------------------------------------------------------------------------
+
+The following 3rd-party ICC profiles may be used by or distributed with
+PhotoPrism. Any information relevant to third-party vendors listed below are
+collected using common, reasonable means.
+
+Date generated: 2025-11-23
+
+--------------------------------------------------------------------------------
+
+Files: a98.icc (compatibleWithAdobeRGB1998.icc)
+Source: OpenICC "compatibleWithAdobeRGB1998.icc" via Debian icc-profiles-free
+URL: https://salsa.debian.org/debian/icc-profiles-free/-/blob/a7a3c11b8a6d3bc2937447183b87dc89de9d2388/icc-profiles-openicc/default_profiles/base/compatibleWithAdobeRGB1998.icc
+License: zlib/libpng
+Checksum (md5): 826a1e13374e3dc34f9872f31ec028c8
+
+The zlib/libpng License
+
+Copyright (c) Graeme Gill <graeme@argyllcms.com>
+
+This software is provided 'as-is', without any express or implied
+warranty. In no event will the authors be held liable for any damages
+arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it
+freely, subject to the following restrictions:
 
-License: Zlib
- The zlib/libpng License
- .
- This software is provided 'as-is', without any express or implied
- warranty. In no event will the authors be held liable for any damages
- arising from the use of this software.
- .
- Permission is granted to anyone to use this software for any purpose,
- including commercial applications, and to alter it and redistribute it
- freely, subject to the following restrictions:
- .
     1. The origin of this software must not be misrepresented; you must not
     claim that you wrote the original software. If you use this software
     in a product, an acknowledgment in the product documentation would be
     appreciated but is not required.
- .
+
     2. Altered source versions must be plainly marked as such, and must not be
     misrepresented as being the original software.
- .
+
     3. This notice may not be removed or altered from any source
     distribution.
- .
- NO WARRANTY
- .
-   BECAUSE THE DATA IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
- FOR THE DATA, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
- OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
- PROVIDE THE DATA "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
- OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
- MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
- TO THE QUALITY AND PERFORMANCE OF THE DATA IS WITH YOU.  SHOULD THE
- DATA PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
- REPAIR OR CORRECTION.
- .
-  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
- WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
- REDISTRIBUTE THE DATA AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
- INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
- OUT OF THE USE OR INABILITY TO USE THE DATA (INCLUDING BUT NOT LIMITED
- TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
- YOU OR THIRD PARTIES OR A FAILURE OF THE DATA TO OPERATE WITH ANY OTHER
- PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
- POSSIBILITY OF SUCH DAMAGES.
+
+The provided ICC Profiles in the package are called DATA in the following
+statement:
+
+                NO WARRANTY
+
+  BECAUSE THE DATA IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE DATA, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE DATA "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE DATA IS WITH YOU.  SHOULD THE
+DATA PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE DATA AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE DATA (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE DATA TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+--------------------------------------------------------------------------------
+
+Files: adobecompat-v2.icc, adobecompat-v4.icc, applecompat-v2.icc, applecompat-v4.icc, cgats001compat-v2-micro.icc, colormatchcompat-v2.icc, colormatchcompat-v4.icc, dci-p3-v4.icc, displayp3-v2-magic.icc, displayp3-v2-micro.icc, displayp3-v4.icc, displayp3compat-v2-magic.icc, displayp3compat-v2-micro.icc, displayp3compat-v4.icc, prophoto-v2-magic.icc, prophoto-v2-micro.icc, prophoto-v4.icc, rec2020-g24-v4.icc, rec2020-v2-magic.icc, rec2020-v2-micro.icc, rec2020-v4.icc, rec2020compat-v2-magic.icc, rec2020compat-v2-micro.icc, rec2020compat-v4.icc, rec601ntsc-v2-magic.icc, rec601ntsc-v2-micro.icc, rec601ntsc-v4.icc, rec601pal-v2-magic.icc, rec601pal-v2-micro.icc, rec601pal-v4.icc, rec709-v2-magic.icc, rec709-v2-micro.icc, rec709-v4.icc, scrgb-v2.icc, sgrey-v2-magic.icc, sgrey-v2-micro.icc, sgrey-v2-nano.icc, sgrey-v4.icc, srgb-v2-magic.icc, srgb-v2-micro.icc, srgb-v2-nano.icc, srgb-v4.icc, widegamutcompat-v2.icc, widegamutcompat-v4.icc
+Source: Compact-ICC-Profiles via Debian icc-profiles-free
+URL: https://salsa.debian.org/debian/icc-profiles-free/-/tree/a7a3c11b8a6d3bc2937447183b87dc89de9d2388/Compact-ICC-Profiles/profiles
+License: CC0-1.0 (Public Domain Dedication)
+Checksums (md5):
+  adobecompat-v2.icc              08220aa4b4e4259ec3c446a35197d89b
+  adobecompat-v4.icc              fbf912760a8d14e496ff389c29c3132d
+  applecompat-v2.icc              21453c734d9364abceacc7ab837019ec
+  applecompat-v4.icc              fc399558e27a0d53748820cff2a98a2b
+  cgats001compat-v2-micro.icc     56a85233ee08fa7527875be36cf426d6
+  colormatchcompat-v2.icc         9f2a755b4b3069f46f4eaef11e24926d
+  colormatchcompat-v4.icc         9e119efb0abaa31e955f8a30eeabc58c
+  dci-p3-v4.icc                   bdedf9e7ad0b93ed8f85f8c3ebdc4223
+  displayp3-v2-magic.icc          6748fcfd56d38770a02c023bbd6d0529
+  displayp3-v2-micro.icc          2615293123ddc4366af3da39455c3d7a
+  displayp3-v4.icc                32dc35d6a113b86cbc31bd1281e3baed
+  displayp3compat-v2-magic.icc    05fb82a702e27438ecec47a2f120cdcd
+  displayp3compat-v2-micro.icc    2ef6c295ac5d05760c1a4cf1668951a3
+  displayp3compat-v4.icc          c34c90451326b183916f05b3ae41d920
+  prophoto-v2-magic.icc           15a31d407cf35662fbe4513f6204bfdf
+  prophoto-v2-micro.icc           445c1a3f3f1a20aab68e76838d3ed334
+  prophoto-v4.icc                 8f4523255234753cd2d3111d8f09b184
+  rec2020-g24-v4.icc              3c7afbfff612d10a10775c167d36b51e
+  rec2020-v2-magic.icc            3b5846fb69faa53ebdfd29061f17b0e3
+  rec2020-v2-micro.icc            13d1e96875c35f7d5ebaf0f6a3d16357
+  rec2020-v4.icc                  297c644758a979abe62349ca1ff416d5
+  rec2020compat-v2-magic.icc      9aa85534e81c275bc0627badf157580a
+  rec2020compat-v2-micro.icc      fa39fc95daece7dcaff18e7265082368
+  rec2020compat-v4.icc            66839229639bb55bc443b490fe302364
+  rec601ntsc-v2-magic.icc         53ee12707ac87a8e3b3452af4a325e29
+  rec601ntsc-v2-micro.icc         af05afec2146917a67445ac6cb5ca61d
+  rec601ntsc-v4.icc               cc57dd6fa3d6f08e43e0f70b5376c00a
+  rec601pal-v2-magic.icc          f706fd528cedcd1c88dac50073112f94
+  rec601pal-v2-micro.icc          d193e01949eb5347b0d16d2b3ccdabcf
+  rec601pal-v4.icc                dd7cd61d6ee14a521c9fb5afa2803e8e
+  rec709-v2-magic.icc             47f09046656a2f0d66117a9c1b15e137
+  rec709-v2-micro.icc             f91edc9f3ff1390c842bd9e8759688b0
+  rec709-v4.icc                   0339e2a70940aefd9237311889d065e6
+  scrgb-v2.icc                    a841263101bdf48fb9b81486f5451f2d
+  sgrey-v2-magic.icc              ef6221686b517e4665480639202dacd5
+  sgrey-v2-micro.icc              ca08451dba57ca1e910330cda37515ad
+  sgrey-v2-nano.icc               57d72e3f6437d65c618ebcdb1f6fa1bd
+  sgrey-v4.icc                    b93b1e31e75243ea08fbdab9e82f7cbe
+  srgb-v2-magic.icc               5967f401f9a54913a283942710cef93c
+  srgb-v2-micro.icc               e8de3a5b44d70610306b0a20225701d1
+  srgb-v2-nano.icc                e060a57b7a057f7f0bdb859b68db60e9
+  srgb-v4.icc                     3c6a277ddee033ad090ba22b8323dcaf
+  widegamutcompat-v2.icc          63c0165987ee94c8c7f2c68749e0418d
+  widegamutcompat-v4.icc          4ccb168ae2f7daa51d3cef7df6fa6f16
+
+--------------------------------------------------------------------------------

internal/thumb/README.md

@@ -0,0 +1,65 @@
+## PhotoPrism — Thumbnails Package
+
+**Last Updated:** November 23, 2025
+
+### Overview
+
+`internal/thumb` builds thumbnails with libvips, handling resize/crop options, color management, metadata stripping, and format export (JPEG/PNG). It is used by PhotoPrism’s workers and CLI to generate cached thumbs consistently.
+
+### Context & Constraints
+
+- Uses libvips via govips; initialization is centralized in `VipsInit`.
+- Works on files or in-memory buffers; writes outputs with `fs.ModeFile`.
+- ICC handling: if a JPEG lacks an embedded profile but sets EXIF `InteroperabilityIndex` (`R03`/Adobe RGB, `R98`/sRGB, `THM`/thumbnail), we embed an Adobe-compatible profile; otherwise we leave color untouched.
+- Metadata is removed from outputs to keep thumbs small.
+
+### Goals
+
+- Produce consistent thumbnails for all configured sizes and resample modes.
+- Preserve color fidelity when cameras signal color space through EXIF interop tags.
+- Keep error paths non-fatal: invalid sizes, missing files, or absent profiles should return errors (not panics).
+
+### Non-Goals
+
+- Serving or caching thumbnails (handled elsewhere).
+- Full ICC workflow management; only minimal embedding for interop-index cases.
+
+### Package Layout (Code Map)
+
+- `vips.go` — main `Vips` entry: load, resize/crop, strip metadata, export.
+- `vips_icc.go` — EXIF InteroperabilityIndex handling and ICC embedding.
+- `icc.go` — lists bundled ICC filenames (`IccProfiles`) and `GetIccProfile` helper.
+- `resample.go`, `sizes.go` — resample options and predefined sizes.
+- `thumb.go` and helpers — naming, caching, file info.
+- Tests live alongside sources (`*_test.go`, fixtures under `testdata/`).
+
+### ICC & Interop Handling
+
+- EXIF `InteroperabilityIndex` codes we honor (per EXIF TagNames and regex.info):
+  - `R03` → Adobe RGB (1998) compatible (`a98.icc`, etc.)
+  - `R98` → sRGB (assumed default; no embed)
+  - `THM` → Thumbnail (treated as sRGB; no embed)
+- If an ICC profile already exists, we skip embedding.
+- Test Files:
+  - `testdata/interop_index.jpg` — R03 interop tag, no ICC (expects Adobe profile embed).
+  - `testdata/interop_index_srgb_icc.jpg` — R03 tag with embedded ICC (must remain unchanged).
+  - `testdata/interop_index_r98.jpg` — R98 interop tag, no ICC (should stay sRGB without embedding).
+  - `testdata/interop_index_thm.jpg` — THM interop tag, no ICC (thumbnail; should remain unchanged).
+- References:
+  - [EXIF TagNames (InteroperabilityIndex)](https://unpkg.com/exiftool-vendored.pl@10.50.0/bin/html/TagNames/EXIF.html)
+  - [Digital-Image Color Spaces: Recommendations and Links](https://regex.info/blog/photo-tech/color-spaces-page7)
+
+### Tests
+
+- Fast scoped: `go test ./internal/thumb -run 'Icc|Vips' -count=1`
+- Full: `go test ./internal/thumb -count=1`
+
+### Lint & Formatting
+
+- Format: `make fmt-go`
+- Lint: `make lint-go` or `golangci-lint run ./internal/thumb/...`
+
+### Notes
+
+- When adding ICC files, place them in `assets/profiles/icc/` and append to `IccProfiles`.
+- Comments for exported identifiers must start with the identifier name (Go style).

internal/thumb/icc.go

@@ -1,21 +1,189 @@
 package thumb
 
 import (
+	"errors"
+	"fmt"
 	"os"
-	"path"
+	"path/filepath"
+	"strings"
 )
 
-/*
-Possible TODO: move this into a shared pkg/ so non-thumb
-consumers can also use it. However, it looks fiddly to hook that
-up to `assets`, so I'm punting on that for now.
-*/
+// Standard ICC profiles located in "assets/profiles/icc".
+const (
+	// IccAdobeRGBCompat is compatible with Adobe RGB (1998).
+	IccAdobeRGBCompat = "a98.icc"
 
-func MustGetAdobeRGB1998Path() string {
-	p := path.Join(IccProfilesPath, "adobe_rgb_compat.icc")
-	_, err := os.Stat(p)
-	if err != nil {
-		panic(err)
-	}
-	return p
+	// IccAdobeRGBCompatV2 is A98C (Adobe RGB 1998 compatible, ICC v2).
+	IccAdobeRGBCompatV2 = "adobecompat-v2.icc"
+	// IccAdobeRGBCompatV4 is A98C (Adobe RGB 1998 compatible, ICC v4).
+	IccAdobeRGBCompatV4 = "adobecompat-v4.icc"
+
+	// IccAppleCompatV2 is APLC (Apple Color Matching compatible, ICC v2).
+	IccAppleCompatV2 = "applecompat-v2.icc"
+	// IccAppleCompatV4 is APLC (Apple Color Matching compatible, ICC v4).
+	IccAppleCompatV4 = "applecompat-v4.icc"
+
+	// IccCgats001CompatV2Micro is uCMY (CGATS.001 compatible CMY, compact).
+	IccCgats001CompatV2Micro = "cgats001compat-v2-micro.icc"
+
+	// IccColorMatchCompatV2 is ACMC (ColorMatch RGB compatible, ICC v2).
+	IccColorMatchCompatV2 = "colormatchcompat-v2.icc"
+	// IccColorMatchCompatV4 is ACMC (ColorMatch RGB compatible, ICC v4).
+	IccColorMatchCompatV4 = "colormatchcompat-v4.icc"
+
+	// IccDciP3V4 is TP3 (DCI‑P3).
+	IccDciP3V4 = "dci-p3-v4.icc"
+
+	// IccDisplayP3V2Magic is sP3 (Display P3, ICC v2 magic).
+	IccDisplayP3V2Magic = "displayp3-v2-magic.icc"
+	// IccDisplayP3V2Micro is uP3 (Display P3, micro).
+	IccDisplayP3V2Micro = "displayp3-v2-micro.icc"
+	// IccDisplayP3V4 is sP3 (Display P3, ICC v4).
+	IccDisplayP3V4 = "displayp3-v4.icc"
+
+	// IccDisplayP3CompatV2Magic is sP3C (Display P3 compatible, ICC v2 magic).
+	IccDisplayP3CompatV2Magic = "displayp3compat-v2-magic.icc"
+	// IccDisplayP3CompatV2Micro is uP3C (Display P3 compatible, micro).
+	IccDisplayP3CompatV2Micro = "displayp3compat-v2-micro.icc"
+	// IccDisplayP3CompatV4 is sP3C (Display P3 compatible, ICC v4).
+	IccDisplayP3CompatV4 = "displayp3compat-v4.icc"
+
+	// IccProPhotoV2Magic is uROM (ProPhoto RGB compact).
+	IccProPhotoV2Magic = "prophoto-v2-magic.icc"
+	// IccProPhotoV2Micro is uROM (ProPhoto RGB micro).
+	IccProPhotoV2Micro = "prophoto-v2-micro.icc"
+	// IccProPhotoV4 is ROMM (ProPhoto/ROMM RGB, ICC v4).
+	IccProPhotoV4 = "prophoto-v4.icc"
+
+	// IccRec2020Gamma24V4 is 2024 (Rec.2020 gamma 2.4, ICC v4).
+	IccRec2020Gamma24V4 = "rec2020-g24-v4.icc"
+	// IccRec2020V2Magic is 2020 (Rec.2020, ICC v2 magic).
+	IccRec2020V2Magic = "rec2020-v2-magic.icc"
+	// IccRec2020V2Micro is u202 (Rec.2020 micro).
+	IccRec2020V2Micro = "rec2020-v2-micro.icc"
+	// IccRec2020V4 is 2020 (Rec.2020, ICC v4).
+	IccRec2020V4 = "rec2020-v4.icc"
+
+	// IccRec2020CompatV2Magic is 202C (Rec.2020 compatible, ICC v2 magic).
+	IccRec2020CompatV2Magic = "rec2020compat-v2-magic.icc"
+	// IccRec2020CompatV2Micro is u20C (Rec.2020 compatible, micro).
+	IccRec2020CompatV2Micro = "rec2020compat-v2-micro.icc"
+	// IccRec2020CompatV4 is 202C (Rec.2020 compatible, ICC v4).
+	IccRec2020CompatV4 = "rec2020compat-v4.icc"
+
+	// IccRec601NtscV2Magic is R601 (Rec.601 NTSC, ICC v2 magic).
+	IccRec601NtscV2Magic = "rec601ntsc-v2-magic.icc"
+	// IccRec601NtscV2Micro is u601 (Rec.601 NTSC, micro).
+	IccRec601NtscV2Micro = "rec601ntsc-v2-micro.icc"
+	// IccRec601NtscV4 is R601 (Rec.601 NTSC, ICC v4).
+	IccRec601NtscV4 = "rec601ntsc-v4.icc"
+
+	// IccRec601PalV2Magic is 601P (Rec.601 PAL, ICC v2 magic).
+	IccRec601PalV2Magic = "rec601pal-v2-magic.icc"
+	// IccRec601PalV2Micro is u60P (Rec.601 PAL, micro).
+	IccRec601PalV2Micro = "rec601pal-v2-micro.icc"
+	// IccRec601PalV4 is 601P (Rec.601 PAL, ICC v4).
+	IccRec601PalV4 = "rec601pal-v4.icc"
+
+	// IccRec709V2Magic is R709 (Rec.709, ICC v2 magic).
+	IccRec709V2Magic = "rec709-v2-magic.icc"
+	// IccRec709V2Micro is u709 (Rec.709, micro).
+	IccRec709V2Micro = "rec709-v2-micro.icc"
+	// IccRec709V4 is R709 (Rec.709, ICC v4).
+	IccRec709V4 = "rec709-v4.icc"
+
+	// IccScRgbV2 is cRGB (scRGB, ICC v2).
+	IccScRgbV2 = "scrgb-v2.icc"
+
+	// IccSGreyV2Magic is sGry (Display P3 compatible gray, ICC v2 magic).
+	IccSGreyV2Magic = "sgrey-v2-magic.icc"
+	// IccSGreyV2Micro is uGry (Display P3 compatible gray, micro).
+	IccSGreyV2Micro = "sgrey-v2-micro.icc"
+	// IccSGreyV2Nano is nGry (Display P3 compatible gray, nano).
+	IccSGreyV2Nano = "sgrey-v2-nano.icc"
+	// IccSGreyV4 is sGry (Display P3 compatible gray, ICC v4).
+	IccSGreyV4 = "sgrey-v4.icc"
+
+	// IccSRgbV2Magic is sRGB (standard sRGB, ICC v2 magic).
+	IccSRgbV2Magic = "srgb-v2-magic.icc"
+	// IccSRgbV2Micro is uRGB (sRGB micro).
+	IccSRgbV2Micro = "srgb-v2-micro.icc"
+	// IccSRgbV2Nano is nRGB (sRGB nano).
+	IccSRgbV2Nano = "srgb-v2-nano.icc"
+	// IccSRgbV4 is sRGB (standard sRGB, ICC v4).
+	IccSRgbV4 = "srgb-v4.icc"
+
+	// IccWideGamutCompatV2 is AWGC (Adobe Wide Gamut compatible, ICC v2).
+	IccWideGamutCompatV2 = "widegamutcompat-v2.icc"
+	// IccWideGamutCompatV4 is AWGC (Adobe Wide Gamut compatible, ICC v4).
+	IccWideGamutCompatV4 = "widegamutcompat-v4.icc"
+)
+
+// IccProfiles lists all bundled ICC profile filenames in one place so tests and
+// callers can iterate or validate the full set shipped in assets/profiles/icc.
+var IccProfiles = []string{
+	IccAdobeRGBCompat,
+	IccAdobeRGBCompatV2,
+	IccAdobeRGBCompatV4,
+	IccAppleCompatV2,
+	IccAppleCompatV4,
+	IccCgats001CompatV2Micro,
+	IccColorMatchCompatV2,
+	IccColorMatchCompatV4,
+	IccDciP3V4,
+	IccDisplayP3V2Magic,
+	IccDisplayP3V2Micro,
+	IccDisplayP3V4,
+	IccDisplayP3CompatV2Magic,
+	IccDisplayP3CompatV2Micro,
+	IccDisplayP3CompatV4,
+	IccProPhotoV2Magic,
+	IccProPhotoV2Micro,
+	IccProPhotoV4,
+	IccRec2020Gamma24V4,
+	IccRec2020V2Magic,
+	IccRec2020V2Micro,
+	IccRec2020V4,
+	IccRec2020CompatV2Magic,
+	IccRec2020CompatV2Micro,
+	IccRec2020CompatV4,
+	IccRec601NtscV2Magic,
+	IccRec601NtscV2Micro,
+	IccRec601NtscV4,
+	IccRec601PalV2Magic,
+	IccRec601PalV2Micro,
+	IccRec601PalV4,
+	IccRec709V2Magic,
+	IccRec709V2Micro,
+	IccRec709V4,
+	IccScRgbV2,
+	IccSGreyV2Magic,
+	IccSGreyV2Micro,
+	IccSGreyV2Nano,
+	IccSGreyV4,
+	IccSRgbV2Magic,
+	IccSRgbV2Micro,
+	IccSRgbV2Nano,
+	IccSRgbV4,
+	IccWideGamutCompatV2,
+	IccWideGamutCompatV4,
+}
+
+// GetIccProfile returns the absolute path to the first requested ICC profile
+// that is present in assets/profiles/icc. It validates existence so callers
+// can embed profiles without risking a panic or missing file error.
+func GetIccProfile(profiles ...string) (string, error) {
+	if len(profiles) == 0 {
+		return "", errors.New("no icc profiles specified")
+	}
+
+	// Find first ICC profile file that exists.
+	for _, p := range profiles {
+		filePath := filepath.Join(IccProfilesPath, p)
+		if info, err := os.Stat(filePath); err == nil && !info.IsDir() {
+			return filePath, nil
+		}
+	}
+
+	return "", fmt.Errorf("no matching icc profiles found (%s)", strings.Join(profiles, ", "))
 }

internal/thumb/icc_test.go

@@ -0,0 +1,55 @@
+package thumb
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/photoprism/photoprism/pkg/fs"
+)
+
+func TestGetIccProfile(t *testing.T) {
+	t.Run("Exists", func(t *testing.T) {
+		profilePath, err := GetIccProfile(IccAdobeRGBCompat)
+		require.NoError(t, err)
+		assert.True(t, fs.FileExists(profilePath))
+	})
+	t.Run("Missing", func(t *testing.T) {
+		originalPath := IccProfilesPath
+		missingDir := t.TempDir()
+
+		IccProfilesPath = missingDir
+
+		t.Cleanup(func() {
+			IccProfilesPath = originalPath
+		})
+
+		profilePath, err := GetIccProfile(IccAdobeRGBCompat)
+
+		assert.Error(t, err)
+		assert.Empty(t, profilePath)
+	})
+}
+
+func TestIccProfiles(t *testing.T) {
+	for _, profile := range IccProfiles {
+		t.Run(profile, func(t *testing.T) {
+			path, err := GetIccProfile(profile)
+
+			require.NoError(t, err)
+			require.True(t, fs.FileExists(path))
+
+			//nolint:gosec // test-only: path is constrained to known profile files in assets
+			data, err := os.ReadFile(path)
+			require.NoError(t, err)
+
+			if len(data) < 40 {
+				t.Fatalf("profile %s too small to contain ICC header", profile)
+			}
+
+			assert.Equal(t, []byte{'a', 'c', 's', 'p'}, data[36:40], "profile %s must contain ICC signature", profile)
+		})
+	}
+}

internal/thumb/vips.go

@@ -75,6 +75,8 @@ func Vips(imageName string, imageBuffer []byte, hash, thumbPath string, width, h
 	case ResampleFillCenter, ResampleResize:
 		crop = vips.InterestingCentre
 		size = vips.SizeBoth
+	default:
+		// Use defaults.
 	}
 
 	if err = vipsSetIccProfileForInteropIndex(img, clean.Log(filepath.Base(imageName))); err != nil {
@@ -161,47 +163,3 @@ func VipsJpegExportParams(width, height int) *vips.JpegExportParams {
 
 	return params
 }
-
-func vipsSetIccProfileForInteropIndex(img *vips.ImageRef, logName string) error {
-
-	// Many cameras will define a JPEG's colour space by setting the InteroperabilityIndex
-	// tag instead of embedding an inline ICC profile.
-	// We detect this and embed explicit icc profiles for thumbs of such images, for the benefit of Vips
-	// and web browsers, none of which pay any attention to the InteropIndex tag.
-	iiFull := img.GetString("exif-ifd4-InteroperabilityIndex")
-	if iiFull == "" {
-		return nil
-	}
-
-	// according to my reading, I think [:4] should be e.g. "R98\x00".
-	// However, vips always returns [:4] = "R98 ", e.g. space instead of null.
-	// I'm pulling [:3] instead to paper over this - the exif spec says "4 bytes
-	// incl null terminator" so I think this is safe.
-	ii := iiFull[:3]
-	log.Tracef("interopindex: %s read exif and got interopindex %s, %s", logName, ii, iiFull)
-
-	if img.HasICCProfile() {
-		log.Debugf("interopindex: %s has both an interop index tag and an embedded ICC profile. ignoring.", logName)
-		return nil
-	}
-
-	fallbackProfile := ""
-	switch ii {
-	case "R03":
-		// adobe rgb
-		fallbackProfile = MustGetAdobeRGB1998Path()
-	case "R98":
-		// srgb
-		// we could logically embed an srgb profile in the image here, but
-		// there's no value in doing so; everything assumes srgb anyway.
-	case "THM":
-		// a thumbnail file. I can't find a ref on what colour space
-		// this is, so I'm assuming without evidence that they are also srgb.
-	default:
-		log.Debugf("interopindex: %s has unknown interop index %s", logName, ii)
-	}
-	if fallbackProfile == "" {
-		return nil
-	}
-	return img.TransformICCProfileWithFallback(fallbackProfile, fallbackProfile) // icc profile gets embedded here
-}

internal/thumb/vips_icc.go

@@ -0,0 +1,78 @@
+package thumb
+
+import (
+	"fmt"
+
+	"github.com/davidbyttow/govips/v2/vips"
+)
+
+// InteroperabilityIndex EXIF codes used by some cameras to hint at the color space.
+// Sources: EXIF TagNames (R03=Adobe RGB, R98=sRGB, THM=thumbnail)
+// https://unpkg.com/exiftool-vendored.pl@10.50.0/bin/html/TagNames/EXIF.html
+// Additional context: https://regex.info/blog/photo-tech/color-spaces-page7
+const (
+	// InteropIndexAdobeRGB is the EXIF code for Adobe RGB (1998) ("R03").
+	InteropIndexAdobeRGB = "R03"
+	// InteropIndexSRGB is the EXIF code for sRGB ("R98").
+	InteropIndexSRGB = "R98"
+	// InteropIndexThumb marks a thumbnail image; treated as sRGB ("THM").
+	InteropIndexThumb = "THM"
+)
+
+// vipsSetIccProfileForInteropIndex embeds an ICC profile when a JPEG declares
+// its color space via the EXIF InteroperabilityIndex tag (e.g., "R03"/Adobe RGB)
+// but lacks an embedded profile. If an ICC profile is already present, it
+// leaves the image untouched.
+func vipsSetIccProfileForInteropIndex(img *vips.ImageRef, logName string) (err error) {
+	// Some cameras signal color space via EXIF InteroperabilityIndex instead of
+	// embedding an ICC profile. Browsers and libvips ignore this tag, so we
+	// inject a matching ICC profile to produce correct thumbnails.
+	iiFull := img.GetString("exif-ifd4-InteroperabilityIndex")
+
+	if iiFull == "" {
+		return nil
+	}
+
+	// EXIF InteroperabilityIndex is 4 bytes including null; libvips returns
+	// a string with a trailing space. Using the first three bytes covers the
+	// meaningful code (e.g., "R03", "R98").
+	if len(iiFull) < 3 {
+		log.Debugf("interopindex: %s has unexpected interop index %q", logName, iiFull)
+		return nil
+	}
+
+	ii := iiFull[:3]
+	log.Tracef("interopindex: %s read exif and got interopindex %s, %s", logName, ii, iiFull)
+
+	if img.HasICCProfile() {
+		log.Debugf("interopindex: %s already has an embedded ICC profile; skipping fallback.", logName)
+		return nil
+	}
+
+	profilePath := ""
+
+	switch ii {
+	case InteropIndexAdobeRGB:
+		// Use Adobe RGB 1998 compatible profile.
+		profilePath, err = GetIccProfile(IccAdobeRGBCompat, IccAdobeRGBCompatV2, IccAdobeRGBCompatV4)
+
+		if err != nil {
+			return fmt.Errorf("interopindex %s: %w", ii, err)
+		}
+	case InteropIndexSRGB:
+		// sRGB: browsers and libvips assume sRGB by default, so no embed needed.
+	case InteropIndexThumb:
+		// Thumbnail file; specification unclear—treat as sRGB and do nothing.
+	default:
+		log.Debugf("interopindex: %s has unknown interop index %s", logName, ii)
+	}
+
+	if profilePath == "" {
+		return nil
+	}
+
+	// Embed ICC profile. govips expects both an input (fallback) and output
+	// profile; using the same path injects the chosen profile when none is
+	// embedded and keeps colors consistent otherwise.
+	return img.TransformICCProfileWithFallback(profilePath, profilePath)
+}

internal/thumb/vips_icc_test.go

@@ -0,0 +1,75 @@
+package thumb
+
+import (
+	"testing"
+
+	"github.com/davidbyttow/govips/v2/vips"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestVipsSetIccProfileForInteropIndex(t *testing.T) {
+	t.Run("PreservesExistingProfile", func(t *testing.T) {
+		VipsInit()
+
+		img, err := vips.LoadImageFromFile("testdata/interop_index_srgb_icc.jpg", VipsImportParams())
+		require.NoError(t, err)
+
+		iiFull := img.GetString("exif-ifd4-InteroperabilityIndex")
+		require.NotEmpty(t, iiFull)
+		require.True(t, img.HasICCProfile())
+
+		originalProfile := img.GetICCProfile()
+		require.NotEmpty(t, originalProfile)
+
+		err = vipsSetIccProfileForInteropIndex(img, "interop_index_srgb_icc.jpg")
+		assert.NoError(t, err)
+		assert.True(t, img.HasICCProfile())
+		assert.Equal(t, originalProfile, img.GetICCProfile())
+	})
+	t.Run("EmbedsAdobeProfileWhenMissing", func(t *testing.T) {
+		VipsInit()
+
+		img, err := vips.LoadImageFromFile("testdata/interop_index.jpg", VipsImportParams())
+		require.NoError(t, err)
+		require.False(t, img.HasICCProfile(), "fixture should have no embedded ICC profile")
+
+		err = vipsSetIccProfileForInteropIndex(img, "interop_index.jpg")
+		assert.NoError(t, err)
+		assert.True(t, img.HasICCProfile(), "Adobe ICC profile should be embedded based on InteropIndex R03")
+		assert.NotEmpty(t, img.GetICCProfile())
+	})
+	t.Run("NoInteropIndexNoop", func(t *testing.T) {
+		VipsInit()
+
+		img, err := vips.LoadImageFromFile("testdata/example.jpg", VipsImportParams())
+		require.NoError(t, err)
+
+		hasICCBefore := img.HasICCProfile()
+		err = vipsSetIccProfileForInteropIndex(img, "example.jpg")
+		assert.NoError(t, err)
+		assert.Equal(t, hasICCBefore, img.HasICCProfile())
+	})
+	t.Run("InteropIndexSRGB_NoEmbed", func(t *testing.T) {
+		VipsInit()
+
+		img, err := vips.LoadImageFromFile("testdata/interop_index_r98.jpg", VipsImportParams())
+		require.NoError(t, err)
+		require.False(t, img.HasICCProfile(), "fixture should have no embedded ICC profile")
+
+		err = vipsSetIccProfileForInteropIndex(img, "interop_index_r98.jpg")
+		assert.NoError(t, err)
+		assert.False(t, img.HasICCProfile(), "sRGB interop index should remain without embedded ICC")
+	})
+	t.Run("InteropIndexThumb_NoEmbed", func(t *testing.T) {
+		VipsInit()
+
+		img, err := vips.LoadImageFromFile("testdata/interop_index_thm.jpg", VipsImportParams())
+		require.NoError(t, err)
+		require.False(t, img.HasICCProfile(), "fixture should have no embedded ICC profile")
+
+		err = vipsSetIccProfileForInteropIndex(img, "interop_index_thm.jpg")
+		assert.NoError(t, err)
+		assert.False(t, img.HasICCProfile(), "THM interop index should remain without embedded ICC")
+	})
+}