diff --git a/src/imageformats/avif.cpp b/src/imageformats/avif.cpp
index 3b29349..6e644d9 100644
--- a/src/imageformats/avif.cpp
+++ b/src/imageformats/avif.cpp
@@ -388,6 +388,9 @@ bool QAVIFHandler::decode_one_frame()
                 case 2: /* AVIF_COLOR_PRIMARIES_UNSPECIFIED */
                     colorspace = QColorSpace(QColorSpace::Primaries::SRgb, q_trc, q_trc_gamma);
                     break;
+                case 9:
+                    colorspace = QColorSpace(QColorSpace::Primaries::Bt2020, q_trc, q_trc_gamma);
+                    break;
                 /* AVIF_COLOR_PRIMARIES_SMPTE432 */
                 case 12:
                     colorspace = QColorSpace(QColorSpace::Primaries::DciP3D65, q_trc, q_trc_gamma);
@@ -740,6 +743,15 @@ bool QAVIFHandler::write(const QImage &image)
                 /* AVIF_TRANSFER_CHARACTERISTICS_LINEAR */
                 avif->transferCharacteristics = (avifTransferCharacteristics)8;
                 break;
+            case QColorSpace::TransferFunction::Gamma:
+                if (qAbs(tmpgrayimage.colorSpace().gamma() - 2.2f) < 0.1f) {
+                    /* AVIF_TRANSFER_CHARACTERISTICS_BT470M */
+                    avif->transferCharacteristics = (avifTransferCharacteristics)4;
+                } else if (qAbs(tmpgrayimage.colorSpace().gamma() - 2.8f) < 0.1f) {
+                    /* AVIF_TRANSFER_CHARACTERISTICS_BT470BG */
+                    avif->transferCharacteristics = (avifTransferCharacteristics)5;
+                }
+                break;
             case QColorSpace::TransferFunction::SRgb:
                 /* AVIF_TRANSFER_CHARACTERISTICS_SRGB */
                 avif->transferCharacteristics = (avifTransferCharacteristics)13;
@@ -754,6 +766,42 @@ bool QAVIFHandler::write(const QImage &image)
                 /* AVIF_TRANSFER_CHARACTERISTICS_UNSPECIFIED */
                 break;
             }
+
+            if (avif->transferCharacteristics == 2) { // in case TransferFunction was not identified yet
+                if (tmpgrayimage.colorSpace().colorModel() == QColorSpace::ColorModel::Gray && lossless) {
+                    avif->colorPrimaries = (avifColorPrimaries)2;
+                    avif->matrixCoefficients = (avifMatrixCoefficients)6;
+
+                    QByteArray iccprofile_gray = tmpgrayimage.colorSpace().iccProfile();
+
+                    if (iccprofile_gray.size() > 0) {
+#if AVIF_VERSION >= 1000000
+                        res = avifImageSetProfileICC(avif, reinterpret_cast<const uint8_t *>(iccprofile_gray.constData()), iccprofile_gray.size());
+                        if (res != AVIF_RESULT_OK) {
+                            qCWarning(LOG_AVIFPLUGIN, "ERROR in avifImageSetProfileICC: %s", avifResultToString(res));
+                            return false;
+                        }
+#else
+                        avifImageSetProfileICC(avif, reinterpret_cast<const uint8_t *>(iccprofile_gray.constData()), iccprofile_gray.size());
+#endif
+                    }
+                } else { // convert to grayscale with SRgb
+                    tmpgrayimage.convertToColorSpace(QColorSpace(QPointF(0.3127f, 0.329f), QColorSpace::TransferFunction::SRgb), QImage::Format_Grayscale16);
+                    switch (tmpgrayimage.format()) {
+                    case QImage::Format_Grayscale8:
+                        save_depth = 8;
+                        break;
+                    case QImage::Format_Grayscale16:
+                        save_depth = 10;
+                        avif->transferCharacteristics = (avifTransferCharacteristics)13;
+                        break;
+                    default:
+                        qCWarning(LOG_AVIFPLUGIN, "Error saving Gray image");
+                        return false;
+                        break;
+                    }
+                }
+            }
         }
 
         if (save_depth > 8) { // QImage::Format_Grayscale16
@@ -838,6 +886,10 @@ bool QAVIFHandler::write(const QImage &image)
                 /* AVIF_MATRIX_COEFFICIENTS_CHROMA_DERIVED_NCL */
                 matrix_to_save = (avifMatrixCoefficients)12;
                 break;
+            case QColorSpace::Primaries::Bt2020:
+                primaries_to_save = (avifColorPrimaries)9;
+                matrix_to_save = (avifMatrixCoefficients)12;
+                break;
             default:
                 /* AVIF_TRANSFER_CHARACTERISTICS_UNSPECIFIED */
                 primaries_to_save = (avifColorPrimaries)2;