Merge pull request opencv#26298 from sturkmen72:avif

Proposed solution for the issue 26297 opencv#26298

closes opencv#26297

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

Author: sturkmen72

CMakeLists.txt

@@ -216,7 +216,7 @@ OCV_OPTION(WITH_1394 "Include IEEE1394 support" OFF
 OCV_OPTION(WITH_AVFOUNDATION "Use AVFoundation for Video I/O (iOS/visionOS/Mac)" ON
   VISIBLE_IF APPLE
   VERIFY HAVE_AVFOUNDATION)
-OCV_OPTION(WITH_AVIF "Enable AVIF support" OFF
+OCV_OPTION(WITH_AVIF "Enable AVIF support" ON
   VERIFY HAVE_AVIF)
 OCV_OPTION(WITH_CAP_IOS "Enable iOS video capture" ON
   VISIBLE_IF IOS

modules/imgcodecs/src/grfmt_avif.cpp

@@ -142,8 +142,7 @@ static constexpr size_t kAvifSignatureSize = 500;
 AvifDecoder::AvifDecoder() {
   m_buf_supported = true;
   channels_ = 0;
-  decoder_ = avifDecoderCreate();
-  decoder_->strictFlags = AVIF_STRICT_DISABLED;
+  decoder_ = nullptr;
 }
 
 AvifDecoder::~AvifDecoder() {
@@ -181,6 +180,11 @@ bool AvifDecoder::checkSignature(const String &signature) const {
 ImageDecoder AvifDecoder::newDecoder() const { return makePtr<AvifDecoder>(); }
 
 bool AvifDecoder::readHeader() {
+  if (decoder_)
+    return true;
+
+  decoder_ = avifDecoderCreate();
+  decoder_->strictFlags = AVIF_STRICT_DISABLED;
   if (!m_buf.empty()) {
     CV_Assert(m_buf.type() == CV_8UC1);
     CV_Assert(m_buf.rows == 1);

modules/imgcodecs/test/test_avif.cpp

@@ -337,11 +337,20 @@ TEST_P(Imgcodecs_Avif_Animation_WriteDecodeSuite, encode_decode) {
   std::vector<unsigned char> buf(size);
   EXPECT_TRUE(file.read(reinterpret_cast<char*>(buf.data()), size));
   file.close();
-  EXPECT_EQ(0, remove(output.c_str()));
   std::vector<cv::Mat> anim;
   ASSERT_TRUE(cv::imdecodemulti(buf, imread_mode_, anim));
 
   ValidateRead(anim_original, anim);
+
+  if (imread_mode_ == IMREAD_UNCHANGED) {
+    ImageCollection collection(output, IMREAD_UNCHANGED);
+    anim.clear();
+    for (auto&& i : collection)
+      anim.push_back(i);
+    ValidateRead(anim_original, anim);
+  }
+
+  EXPECT_EQ(0, remove(output.c_str()));
 }
 
 INSTANTIATE_TEST_CASE_P(