TIFF file format

The TIFF v6.0 format described by FLML.

[# TIFF v6.0]
#Image File Header
[2]<char>(name="byte order"; id="byte_oder"; choices={['I','I'], ['M','M']})
[1]<uint16; =42>(name="magic number")
[1]<uint32; :offset_to_first_IFD>(id="offset_to_first_IFD")

if (offset_to_first_IFD >= 8) {
    tag_info = {}
    goto (offset_to_first_IFD) {
        [1]<uint16; :entry_num>(name="entry number")
        [entry_num]{
            [1]<uint16; :tag_id>
            [1]<uint16; :tag_data_type>
            [1]<uint32; :tag_data_type_count>
            [4]<byte; :value_or_offset>
            key, value = get_tag_info(tag_id, tag_data_type, tag_data_type_count, value_or_offset);
            tag_info[key] = value;
        }
        [1]<uint32; offset_to_next_IFD>
    }
    i = 0;
    for (stripoffset in tag_info["StripOffsets"]) {
        goto (stripoffset) {
            [tag_info["StripByteCounts"][i] / (sum(tag_info["BitsPerSample"]) / 8) / tag_info["ImageWidth"]]{
                [tag_info[ImageWidth]]{
                    [sum(tag_info["BitsPerSample"]) / 8]<byte>
                }
            }
            [tag_info["StripByteCounts"][i]] {
                [3]<byte>
            }
        }
        i += 1;
    }
}


fun get_tag_data_type(data_type) {
    if (data_type == 1) {
        data_type = [1, 1, "uint8"];
    } elif (data_type == 2) {
        data_type = [1, 1, "char"];
    } elif (data_type == 3) {
        data_type = [2, 2, "uint16"];
    } elif (data_type == 4) {
        data_type = [4, 4, "uint32"];
    } elif (data_type == 5) {
        data_type = [8, 4, "uint32"];
    } elif (data_type == 6) {
        data_type = [1, 1, "int8"];
    } elif (data_type == 7) {
        data_type = [1, 1, "byte"];
    } elif (data_type == 8) {
        data_type = [2, 2, "int16"];
    } elif (data_type == 9) {
        data_type = [4, 4, "int32"];
    } elif (data_type == 10) {
        data_type = [8, 4, "int32"];
    } elif (data_type == 11) {
        data_type = [4, 4, "float"];
    } elif (data_type == 12) {
        data_type == [8, 8, "double"];
    } else {
        raise Exception("unkown data type");
    }
    return data_type;
}


fun byte_to_int(bytes_arr, int_type, int_bytes_len, int_num) {
    int_s = [];
    if (int_type == "uint") {
        for (i = 0; i < int_num; i++) {
            n = 0;
            for (j = 0; j < int_bytes_len; j++) {
                n += byte_arr[i * int_bytes_len + j] * 255**j;
            }
        }
    }
    return int_s;
}

fun get_tag_info(tag_id, tag_data_type, tag_data_type_count, value_or_offset) {
    if (tag_id == 256) {
        tag_data_type = get_tag_data_type(tag_data_type); #[2, 2, "uint16"]
        return "ImageWidth", byte_to_int(value_or_offset, "uint", tag_data_type[1], 1)[0]
    }
    elif (tag_id == 257) {
        tag_data_type = get_tag_data_type(tag_data_type);
        return "ImageLength", byte_to_int(value_or_offset, "uint", tag_data_type[1], 1)[0];
    }
    elif (tag_id == 258) {
        tag_data_type = get_tag_data_type(tag_data_type);
        if (tag_data_type[0] * tag_data_type_count > 4) {
            seek_pos = byte_to_int(value_or_offset, "uint", tag_data_type[1], 1)[0];
            fileself.seek(seek_pos);
            return "BitsPerSample", fileself.read(tag_data_type[1] * tag_data_type_count);
        }
        else {
            return "BitsPerSample", byte_to_int(value_or_offset, "uint", tag_data_type[1], tag_data_type_count);
        }
    }
    elif (tag_id == 259) {
        return "Compression", byte_to_int(value_or_offset, "uint", 2, 1)[0];
    }
    elif (tag_id == 262) {
        return "PhotometricInterpretation", byte_to_int(value_or_offset, "uint", 2, 1)[0];
    }
    elif (tag_id == 273) {
        tag_data_type = get_tag_data_type(tag_data_type);
        if (tag_data_type[0] * tag_data_type_count > 4) {
            seek_pos = byte_to_int(value_or_offset, "uint" tag_data_type[1], 1)[0];
            fileself.seek(seek_pos);
            bytes_arr = fileself.read(tag_data_type[1] * tag_data_type_count);
            return "StripOffsets", byte_to_int(bytes_arr, "uint", tag_data_type[1], tag_data_type_count);
        }
        else {
            return "StripOffsets", byte_to_int("uint", value_or_offset, 2, tag_data_type_count);
        }
    }
    elif (tag_id == 274) {
        return "SamplesPerPixel", byte_to_int(value_or_offset, "uint", 2, 1)[0];
    }
    elif (tag_id == 278) {
        return "RowsPerStrip", byte_to_int(value_or_offset, "uint", 2, 1)[0];
    }
    elif (tag_id == 279) {
        tag_data_type = get_tag_data_type(tag_data_type);
        if (tag_data_type[0] * tag_data_type_count > 4) {
            seek_pos = byte_to_int("uint", value_or_offset, tag_data_type[1], 1)[0];
            fileself.seek(seek_pos);
            byte_arr = fileself.read(tag_data_type[1] * tag_data_type_count);
            return "StripOffsets", byte_to_int(byte_arr, "uint", tag_data_type[1], tag_data_type_count);
        }
        else {
            return "StripOffsets", byte_to_int(value_or_offset, "uint", 2, tag_data_type_count);
        }
    }
}

[#Notes
    byte_oder:
        Two char to indicate byte order, can be "II" for little ednian
        or "MM" for big endian.

    offset_to_first_IFD:
        The offset to the first IFD(Image File Directory).

]

[#Reference
1. https://www.fileformat.info/format/tiff/egff.htm

]