trading_agent.attachments.image_preparer

Checks uploaded pictures, and prepares them for the models.

A phone photo is often 4000 pixels wide and several megabytes, while the models see detail only up to about 1568 pixels on the long side and charge context for every pixel up to that. Before a picture goes to a model it is turned upright by its EXIF orientation, shrunk to at most 1568 pixels on its long side, and saved as a JPEG, or as a PNG when it has transparency. The uploaded file itself is kept unchanged.

Typical usage example:

preparer = ImagePreparer() media_type = preparer.check(path) image = preparer.prepare(path)

ImageError

Bases: ValueError

A file is not a picture that can be used.

ImagePreparer

Checks pictures and resizes them for the models.

check

check(path)

Checks that a file is a PNG, JPEG, WebP or GIF picture.

Parameters:

Name	Type	Description	Default
path	Path	The file.	required

Returns:

Type	Description
str	Its media type, from the file's contents rather than its name.

Raises:

Type	Description
ImageError	The file is not one of those pictures, or is damaged.

Source code in src/trading_agent/attachments/image_preparer.py

def check(self, path: Path) -> str:
    """Checks that a file is a PNG, JPEG, WebP or GIF picture.

    Args:
        path (Path): The file.

    Returns:
        str: Its media type, from the file's contents rather than its name.

    Raises:
        ImageError: The file is not one of those pictures, or is damaged.
    """
    try:
        with PIL.Image.open(path) as picture:
            picture_format = picture.format
            picture.verify()
    except _OPEN_ERRORS as error:
        raise ImageError(
            f'it is not a picture that can be read ({type(error).__name__})'
        ) from error
    if picture_format not in _MEDIA_TYPES:
        raise ImageError(
            f'{picture_format} pictures are not accepted; send PNG, JPEG, WebP or GIF'
        )
    return _MEDIA_TYPES[picture_format]

prepare

prepare(path)

Makes the copy of a picture that a model is sent.

Parameters:

Name	Type	Description	Default
path	Path	The picture.	required

Returns:

Type	Description
MessageImage | None	The upright, resized picture, or None when the file is gone or cannot be read.

Source code in src/trading_agent/attachments/image_preparer.py

def prepare(self, path: Path) -> messages.MessageImage | None:
    """Makes the copy of a picture that a model is sent.

    Args:
        path (Path): The picture.

    Returns:
        messages.MessageImage | None: The upright, resized picture, or None when the file is gone or cannot be read.
    """
    try:
        with PIL.Image.open(path) as opened:
            picture = PIL.ImageOps.exif_transpose(opened)
            picture.load()
    except _OPEN_ERRORS:
        return None
    picture.thumbnail(
        (
            _LONGEST_SIDE,
            _LONGEST_SIDE,
        )
    )
    output = io.BytesIO()
    if self._has_transparency(picture):
        picture.convert('RGBA').save(output, format='PNG', optimize=True)
        return messages.MessageImage('image/png', output.getvalue())
    picture.convert('RGB').save(
        output, format='JPEG', quality=_JPEG_QUALITY
    )
    return messages.MessageImage('image/jpeg', output.getvalue())