@asmorkalov could you take a look at this PR. it is not urgent but maybe merging it before 4.12 release will be useful

@asmorkalov sorry to bother. there is a last minute fix for an issue.

@asmorkalov OK, i have more time to better improvements.

✅ DECODER_OK = 0
Meaning:
The decoder has successfully completed its operation (e.g., reading the header or data). Everything is working as expected.

In ImageCollection:
The image is properly loaded and ready to be used (e.g., displayed, processed, or added to a collection).

⚠️ DECODER_UNINITIALIZED = 1
Meaning:
The decoder object was not properly initialized before use.
This often means some required setup (e.g., calling init() or setting a source) was skipped.

In ImageCollection:
This might occur if an image entry is added before setting a path, or if the decoder instance was used too early.

❌ DECODER_SOURCE_NOT_OPENED = 2
Meaning:
The decoder couldn’t open the source, such as a file path, memory buffer, or stream.

In ImageCollection:
This happens if:

The file doesn’t exist.

It’s unreadable (permissions issue).

It’s empty or corrupted.

The image will likely be skipped or flagged as a loading error.

❓ DECODER_UNKNOWN_SOURCE_FORMAT = 3
Meaning:
The source was opened, but the image format couldn’t be recognized or is unsupported.

In ImageCollection:
Examples:

A file with a .jpg extension that is actually a text file.

A valid file of a format not supported by the decoder (e.g., .tiff in a system that only supports PNG and JPEG).

🧱 DECODER_READ_HEADER_FAILED = 4
Meaning:
An error occurred while parsing the image header. This part usually contains size, color type, number of channels, etc.

In ImageCollection:

Indicates the image file is partially damaged or incorrectly encoded.

Common in corrupt downloads or truncated files.

💥 DECODER_READ_DATA_FAILED = 5
Meaning:
The image header was okay, but the decoder failed to read the actual image data (pixels, animation frames, etc.).

In ImageCollection:

Could occur during multi-frame extraction (e.g., animated WebP, GIF).

Or due to allocation issues (e.g., insufficient memory).

The image might show up with correct metadata but no pixel content.

another option is ( maybe simple is better )

class CV_EXPORTS_W ImageCollection {
public:
enum Status
{
    OK = 0,                      ///< No error.
    UNINITIALIZED = 1,           ///< The object has not been properly initialized.
    SOURCE_ERROR = 2,            ///< Failed to open or recognize the input source.
    READ_ERROR = 3               ///< Failed to read header or image data.
};

ImageCollection::Status::OK
ImageCollection::Status::UNINITIALIZED
ImageCollection::Status::SOURCE_ERROR
ImageCollection::Status::READ_ERROR