deps: libheif 1.21 support (AcademySoftwareFoundation#4992)

Starting with 1.21, libheif seems to change behavior: When no CICP
metadata is present, libheif now returns 2,2,2 (all unspecified) on
read. OIIO convention, though, is to not set the attribute if valid CICP
data is not in the file.

---------

Signed-off-by: Larry Gritz <lg@larrygritz.com>

Author: lgritz

INSTALL.md

@@ -64,7 +64,7 @@ NEW or CHANGED MINIMUM dependencies since the last major release are **bold**.
      * giflib >= 5.0 (tested through 5.2.2)
  * If you want support for HEIF/HEIC or AVIF images:
      * libheif >= 1.11 (1.16 required for correct orientation support,
-       tested through 1.20.2)
+       tested through 1.21.1)
      * libheif must be built with an AV1 encoder/decoder for AVIF support.
  * If you want support for DICOM medical image files:
      * DCMTK >= 3.6.1 (tested through 3.6.9)

src/heif.imageio/heifinput.cpp

@@ -287,7 +287,14 @@ HeifInput::seek_subimage(int subimage, int miplevel)
             m_ihandle.get_raw_image_handle(), &nclx);
 
         if (nclx) {
-            if (err.code == heif_error_Ok) {
+            // When CICP metadata is not present in the file, libheif returns
+            // unspecified since v1.21. Ignore it then.
+            if (err.code == heif_error_Ok
+                && !(nclx->color_primaries == heif_color_primaries_unspecified
+                     && nclx->transfer_characteristics
+                            == heif_transfer_characteristic_unspecified
+                     && nclx->matrix_coefficients
+                            == heif_matrix_coefficients_unspecified)) {
                 const int cicp[4] = { int(nclx->color_primaries),
                                       int(nclx->transfer_characteristics),
                                       int(nclx->matrix_coefficients),