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Merged
lgritz merged 10 commits into from
Sep 13, 2025
Merged

feat: CICP metadata support for PNG #4746

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200c3c5
feat: Add CICP support to PNG plugin
zachlewis May 7, 2025
3ebb288
feat: Add ImageSpec::set_cicp functions and oiiotool --cicp option
zachlewis May 11, 2025
bb91251
testing: add tests for PNG, oiiotool, and python
zachlewis Sep 1, 2025
378584d
fix: force set_colorspace() to erase the `CICP` attribute
zachlewis Sep 12, 2025
7c2285b
Update testsuite/png/run.py
zachlewis Sep 13, 2025
252986f
Update src/png.imageio/png_pvt.h
zachlewis Sep 13, 2025
a30f4e4
Update src/png.imageio/png_pvt.h
zachlewis Sep 13, 2025
574dfa3
docs: Update oiiotool, stdmetadata.rst, ImageInput::supports: `cicp` nfo
zachlewis Sep 13, 2025
f957d6e
Update src/doc/stdmetadata.rst
zachlewis Sep 13, 2025
652c0e5
Update src/doc/stdmetadata.rst
zachlewis Sep 13, 2025
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3 changes: 3 additions & 0 deletions src/include/OpenImageIO/imageio.h
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Expand Up @@ -2527,6 +2527,9 @@ class OIIO_API ImageOutput {
/// Does this format allow 0x0 sized images, i.e. an image file
/// with metadata only and no pixels?
///
/// - `"cicp"` :
/// Does this format support embedding CICP metadata?
///
Comment on lines +2533 to +2535
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@lgritz lgritz Sep 13, 2025

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Does a similar comment need to go in ImageInput::supports so that it's documented for both?

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@zachlewis zachlewis Sep 13, 2025

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It sure does! On it.

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@zachlewis zachlewis Sep 13, 2025

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need to make sure I've appropriately documented in oiiotool.rst and stdmetadata.rst as well.

/// This list of queries may be extended in future releases. Since this
/// can be done simply by recognizing new query strings, and does not
/// require any new API entry points, addition of support for new
Expand Down
2 changes: 2 additions & 0 deletions src/libOpenImageIO/formatspec.cpp
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Expand Up @@ -1295,6 +1295,8 @@ void
ImageSpec::set_colorspace(string_view colorspace)
{
ColorConfig::default_colorconfig().set_colorspace(*this, colorspace);
// Invalidate potentially contradictory metadata
erase_attribute("CICP");
}


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57 changes: 57 additions & 0 deletions src/oiiotool/oiiotool.cpp
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Expand Up @@ -2248,6 +2248,60 @@ icc_read(Oiiotool& ot, cspan<const char*> argv)
}


// Set, modify, or remove the top image's CICP (ITU-T H.273) metadata.
class OpSetCICP final : public OiiotoolOp {
public:
OpSetCICP(Oiiotool& ot, string_view opname, cspan<const char*> argv)
: OiiotoolOp(ot, opname, argv, 1)
{
inplace(true); // This action operates in-place
cicp = args(1);
}
OpSetCICP(Oiiotool& ot, string_view opname, int argc, const char* argv[])
: OpSetCICP(ot, opname, { argv, span_size_t(argc) })
{
}
bool setup() override
{
ir(0)->metadata_modified(true);
return true;
}
bool impl(span<ImageBuf*> img) override
{
// Because this is an in-place operation, img[0] is the same as
// img[1].
if (cicp.empty()) {
img[0]->specmod().erase_attribute("CICP");
return true;
}
std::vector<int> vals { 0, 0, 0, 1 };
auto p = img[0]->spec().find_attribute("CICP",
TypeDesc(TypeDesc::INT, 4));
if (p) {
const int* existing = static_cast<const int*>(p->data());
for (int i = 0; i < 4; ++i)
vals[i] = existing[i];
}
Strutil::extract_from_list_string<int>(vals, cicp);
img[0]->specmod().attribute("CICP", TypeDesc(TypeDesc::INT, 4),
vals.data());
return true;
}

private:
string_view cicp;
};


// --cicp
static void
action_cicp(Oiiotool& ot, cspan<const char*> argv)
{
OpSetCICP op(ot, "cicp", argv);
op();
}



// --colorconfig
static void
Expand Down Expand Up @@ -7173,6 +7227,9 @@ Oiiotool::getargs(int argc, char* argv[])
ap.arg("--iccread %s:FILENAME")
.help("Add the contents of the file to the top image as its ICC profile")
.OTACTION(icc_read);
ap.arg("--cicp %s:CICP")
.help("Set or modifiy CICP metadata for supporting output formats (e.g., \"12,16,0,1\")") //; selectively persist existing values if not specified (e.g., \",,,0\")")
.OTACTION(action_cicp);
// clang-format on

if (ap.parse_args(argc, (const char**)argv) < 0) {
Expand Down
31 changes: 28 additions & 3 deletions src/png.imageio/png_pvt.h
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Expand Up @@ -40,7 +40,7 @@ For further information see the following mailing list threads:
OIIO_PLUGIN_NAMESPACE_BEGIN

#define ICC_PROFILE_ATTR "ICCProfile"

#define CICP_ATTR "CICP"

namespace PNG_pvt {

Expand Down Expand Up @@ -224,7 +224,7 @@ read_info(png_structp& sp, png_infop& ip, int& bit_depth, int& color_type,
int srgb_intent;
double gamma = 0.0;
if (png_get_sRGB(sp, ip, &srgb_intent)) {
spec.set_colorspace("srgb_rec709_scene");
spec.attribute("oiio:ColorSpace", "srgb_rec709_scene");
} else if (png_get_gAMA(sp, ip, &gamma) && gamma > 0.0) {
// Round gamma to the nearest hundredth to prevent stupid
// precision choices and make it easier for apps to make
Expand All @@ -235,7 +235,7 @@ read_info(png_structp& sp, png_infop& ip, int& bit_depth, int& color_type,
set_colorspace_rec709_gamma(spec, g);
} else {
// If there's no info at all, assume sRGB.
set_colorspace(spec, "srgb_rec709_scene");
spec.attribute("oiio:ColorSpace", "srgb_rec709_scene");
}

if (png_get_valid(sp, ip, PNG_INFO_iCCP)) {
Expand Down Expand Up @@ -326,6 +326,16 @@ read_info(png_structp& sp, png_infop& ip, int& bit_depth, int& color_type,

interlace_type = png_get_interlace_type(sp, ip);

#ifdef PNG_cICP_SUPPORTED
{
png_byte pri = 0, trc = 0, mtx = 0, vfr = 0;
if (png_get_cICP(sp, ip, &pri, &trc, &mtx, &vfr)) {
int cicp[4] = { pri, trc, mtx, vfr };
spec.attribute(CICP_ATTR, TypeDesc(TypeDesc::INT, 4), cicp);
}
}
#endif

#ifdef PNG_eXIf_SUPPORTED
// Recent version of PNG and libpng (>= 1.6.32, I think) have direct
// support for Exif chunks. Older versions don't support it, and I'm not
Expand Down Expand Up @@ -713,6 +723,21 @@ write_info(png_structp& sp, png_infop& ip, int& color_type, ImageSpec& spec,
(png_uint_32)(yres * scale), unittype);
}

#ifdef PNG_cICP_SUPPORTED
const ParamValue* p = spec.find_attribute(CICP_ATTR,
TypeDesc(TypeDesc::INT, 4));
if (p) {
const int* int_vals = static_cast<const int*>(p->data());
png_byte vals[4];
for (int i = 0; i < 4; ++i)
vals[i] = static_cast<png_byte>(int_vals[i]);
if (setjmp(png_jmpbuf(sp))) // NOLINT(cert-err52-cpp)
return "Could not set PNG cICP chunk";
// libpng will only write the chunk if the third byte is 0
png_set_cICP(sp, ip, vals[0], vals[1], (png_byte)0, vals[3]);
}
#endif

#ifdef PNG_eXIf_SUPPORTED
std::vector<char> exifBlob;
encode_exif(spec, exifBlob, endian::big);
Expand Down
9 changes: 8 additions & 1 deletion src/png.imageio/pnginput.cpp
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Expand Up @@ -18,7 +18,14 @@ class PNGInput final : public ImageInput {
const char* format_name(void) const override { return "png"; }
int supports(string_view feature) const override
{
return (feature == "ioproxy" || feature == "exif");
return (feature == "ioproxy"
#ifdef PNG_eXIf_SUPPORTED
|| feature == "exif"
#endif
#ifdef PNG_cICP_SUPPORTED
|| feature == "cicp"
#endif
);
}
bool valid_file(Filesystem::IOProxy* ioproxy) const override;
bool open(const std::string& name, ImageSpec& newspec) override;
Expand Down
3 changes: 3 additions & 0 deletions src/png.imageio/pngoutput.cpp
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Expand Up @@ -24,6 +24,9 @@ class PNGOutput final : public ImageOutput {
return (feature == "alpha" || feature == "ioproxy"
#ifdef PNG_eXIf_SUPPORTED
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|| feature == "exif"
#endif
#ifdef PNG_cICP_SUPPORTED
|| feature == "cicp"
#endif
);
}
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16 changes: 16 additions & 0 deletions testsuite/png/ref/out-libpng15.txt
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Expand Up @@ -26,6 +26,10 @@ Reading exif.png
exif.png : 64 x 64, 3 channel, uint8 png
SHA-1: 7CB41FEA50720B48BE0C145E1473982B23E9AB77
channel list: R, G, B
Exif:ExifVersion: "0230"
Exif:FlashPixVersion: "0100"
Exif:FocalLength: 45.7 (45.7 mm)
Exif:WhiteBalance: 0 (auto)
oiio:ColorSpace: "srgb_rec709_scene"
alphagamma:
1 x 1, 4 channel, float png
Expand Down Expand Up @@ -86,5 +90,17 @@ gimp_gradient:
Monochrome: No
smallalpha.png : 1 x 1, 4 channel, uint8 png
Pixel (0, 0): 240 108 119 1 (0.94117653 0.42352945 0.4666667 0.003921569)
cicp:
16 x 16, 4 channel, float png
channel list: R, G, B, A
oiio:ColorSpace: "srgb_rec709_scene"
removed_cicp:
16 x 16, 4 channel, float png
channel list: R, G, B, A
oiio:ColorSpace: "srgb_rec709_scene"
remove_cicp_via_set_colorspace:
16 x 16, 4 channel, float png
channel list: R, G, B, A
oiio:ColorSpace: "g22_rec709_display"
Comparing "test16.png" and "ref/test16.png"
PASS
13 changes: 13 additions & 0 deletions testsuite/png/ref/out.txt
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Expand Up @@ -90,5 +90,18 @@ gimp_gradient:
Monochrome: No
smallalpha.png : 1 x 1, 4 channel, uint8 png
Pixel (0, 0): 240 108 119 1 (0.94117653 0.42352945 0.4666667 0.003921569)
cicp:
16 x 16, 4 channel, float png
channel list: R, G, B, A
CICP: 1, 13, 0, 1
oiio:ColorSpace: "srgb_rec709_scene"
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removed_cicp:
16 x 16, 4 channel, float png
channel list: R, G, B, A
oiio:ColorSpace: "srgb_rec709_scene"
remove_cicp_via_set_colorspace:
16 x 16, 4 channel, float png
channel list: R, G, B, A
oiio:ColorSpace: "g22_rec709_display"
Comparing "test16.png" and "ref/test16.png"
PASS
Binary file modified testsuite/png/ref/test16.png
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12 changes: 11 additions & 1 deletion testsuite/png/run.py
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Expand Up @@ -32,5 +32,15 @@
command += oiiotool ("--pattern fill:color=0.00235,0.00106,0.00117,0.0025 1x1 4 -d uint8 -o smallalpha.png")
command += oiiotool ("--no-autopremult --dumpdata smallalpha.png")

outputs = [ "test16.png", "out.txt" ]
# Test embedding CICP metadata in PNG files
command += oiiotool ("-i test16.png --cicp 1,13 -o test16.png")
command += oiiotool ("-echo cicp: test16.png --eraseattrib Software --printinfo")
# FIXME: The following test fails on Windows
# Workaround is to avoid partial modifications and always specify all CICP values
# command += oiiotool ("-echo modified_cicp: test16.png --eraseattrib Software --cicp \",,,0\" --printinfo")
command += oiiotool ("-echo removed_cicp: test16.png --eraseattrib Software --cicp \"\" --printinfo")

# Test that "set_colorspace" removes CICP metadata
command += oiiotool ("-echo remove_cicp_via_set_colorspace: test16.png --eraseattrib Software --cicp 1,13 --iscolorspace g22_rec709_display --printinfo")

outputs = [ "test16.png", "out.txt" ]
13 changes: 7 additions & 6 deletions testsuite/python-imagespec/ref/out.txt
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Expand Up @@ -74,20 +74,20 @@ channelformat(1) = uint8
get_int_attribute('foo_int') retrieves 14
get_int_attribute('foo_int',21) with default retrieves 14
get_int_attribute('foo_no',23) retrieves 23
get_float_attribute('foo_float') retrieves 3.1400001049
get_float_attribute('foo_float') retrieves 3.140000104904175
get_float_attribute('foo_float_no') retrieves 0.0
get_float_attribute('foo_float_no',2.7) retrieves 2.70000004768
get_float_attribute('foo_float_no',2.7) retrieves 2.700000047683716
Comment on lines +77 to +79
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@lgritz lgritz Sep 2, 2025

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Why did these change?

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@lgritz lgritz Sep 2, 2025

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I suspect this is an artifact of the weirdo merge, maybe pulling in some things from other branches that you didn't intend.

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@zachlewis zachlewis Sep 9, 2025

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Mmmm.... unfortunately, I made these changes four months ago, and I forgot to say why exactly in the commit :(
I believe one or more of the MacOS runners were choking on the precision differences; but it's definitely possible the tests were only failing on my local machine, and these were changes I hadn't intended to commit...

Should I revert these changes and see if stuff breaks?

get_string_attribute('foo_str') retrieves blah
get_string_attribute('foo_str_no') retrieves
get_string_attribute('foo_str_no','xx') retrieves xx

getattribute('foo_int') retrieves 14
getattribute('foo_float') retrieves 3.1400001049
getattribute('foo_float') retrieves 3.140000104904175
getattribute('foo_str') retrieves blah
getattribute('foo_vector') retrieves (1.0, 0.0, 11.0)
getattribute('foo_matrix') retrieves (1.0, 0.0, 0.0, 0.0, 0.0, 2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 2.0, 3.0, 1.0)
getattribute('foo_no') retrieves None
getattribute('smpte:TimeCode') retrieves (18356486L, 4294967295L)
getattribute('smpte:TimeCode') retrieves (18356486, 4294967295)
getattribute('ucarr') retrieves [49 50 51 0 0 97 98 99 1 88]
getattribute('unknown') retrieves None
s.get('foo_int') = 14
Expand All @@ -107,13 +107,13 @@ extra_attribs size is 10
"blah"
1 foo_int int 14
14
2 foo_float float 3.1400001049
2 foo_float float 3.140000104904175
3.14
3 foo_vector vector (1.0, 0.0, 11.0)
1, 0, 11
4 foo_matrix matrix (1.0, 0.0, 0.0, 0.0, 0.0, 2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 1.0, 2.0, 3.0, 1.0)
1, 0, 0, 0, 0, 2, 0, 0, 0, 0, 1, 0, 1, 2, 3, 1
5 smpte:TimeCode timecode (18356486L, 4294967295L)
5 smpte:TimeCode timecode (18356486, 4294967295)
01:18:19:06
6 ucarr uint8[10] [49 50 51 0 0 97 98 99 1 88]
49, 50, 51, 0, 0, 97, 98, 99, 1, 88
Expand Down Expand Up @@ -206,6 +206,7 @@ Testing set_colorspace:
after set_colorspace('sRGB'): sRGB
after set_colorspace(''):


Testing global attribute store/retrieve:
get_string_attribute plugin_searchpath : perfect
get_int_attribute plugin_searchpath : 0
Expand Down
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