JPEG Non-Image Data Structure

JPEG metadata structure is framed in several levels:

See JPEG level. containing all JPEG metadata,
See JPEG marker segment levels. containing metadata of each particular JPEG marker segment.

JPEG Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"JPEG-JFIF"	ImGearFormats.JPG	Tree
JPEG marker segment levels

JPEG Marker Segment Levels

The following JPEG marker segments metadata are supported:

See Frame marker segment level. - SOF0, SOF1, SOF2 and SOF3 (read only)
See Frame component level.
See Scan marker segment level. - SOS (read only)
See Scan component level.
See Define-quantization-table marker segment level. - DQT (read only)
See Define-quantization-table table level.
See Define-Huffman-tables marker segment level. - DHT (read only)
See Define-Huffman-table table level.
See Comment marker segment level. - COM (read/write),
See Application marker segment level. - APP0-APP15 (read/write).

Segment level markers are described in the tables below.

Frame Marker Segment Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"Precision"	ImGearJPEGTagIDs. FRAME_PRECISION	Leaf	UINT8		1	TRUE
"Lines"	ImGearJPEGTagIDs. FRAME_LINES	Leaf	UINT16		1	TRUE
"SamplesPerLine"	ImGearJPEGTagIDs. FRAME_SAMPLES_PER_LINE	Leaf	UINT16		1	TRUE
"NumberOfComponents"	ImGearJPEGTagIDs. FRAME_NUMBER_OF_COMPONENTS	Leaf	UINT8	<n>	1	TRUE
Frame component level 1	ImGearJPEGTagIDs. FRAME_COMPONENT_SPEC	Tree
...
Frame component level <n>	ImGearJPEGTagIDs. FRAME_COMPONENT_SPEC	Tree

Frame Component Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"Identifier"	ImGearJPEGTagIDs. FRAME_COMPONENT_ID	Leaf	UINT	<Component No.>	1	TRUE
HVSamplingFactors	ImGearJPEGTagIDs. FRAME_COMPONENT_HV_SAMPLING	Leaf	UINT		1	TRUE
"QuantizationNumber"	ImGearJPEGTagIDs. FRAME_COMPONENT_QUANT_SELECTOR	Leaf	UINT		1	TRUE

Note:: <Component No.> is frame component identifier of appropriate component.

Scan Marker Segment Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"ComponentNumber"	ImGearJPEGTagIDs. SCAN_COMPONENT_NUMBER	Leaf	UINT8	<n>	1	TRUE
Scan component level 1	ImGearJPEGTagIDs.SCAN_COMPONENT	Tree

Scan component level <n>	ImGearJPEGTagIDs.SCAN_COMPONENT	Tree
"SpectralStart"	ImGearJPEGTagIDs.SCAN_SP_START	Leaf	UINT8		1	TRUE
"SpectralEnd"	ImGearJPEGTagIDs.SCAN_SP_END	Leaf	UINT8			TRUE
"AH_AL"	ImGearJPEGTagIDs.SCAN_AH_AL	Leaf	UINT8			TRUE

Scan Component Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"Selector"	ImGearJPEGTagIDs. SCAN_SELECTOR	Leaf	UINT8		1	TRUE
"DC_AC"	ImGearJPEGTagIDs. SCAN_DC_AC	Leaf	UINT8		1	TRUE

Define-Quantization-Table Marker Segment Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"QuantizationTable"	ImGearJPEGTagIDs.QUANT_TABLE	Tree

"QuantizationTable"	ImGearJPEGTagIDs.QUANT_TABLE	Tree

Define-Quantization-Table Table Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"Descriptor"	ImGearJPEGTagIDs. QUANT_TABLE_DESCRIPTOR	Leaf	UINT8			TRUE
"Elements"	ImGearJPEGTagIDs. QUANT_TABLE_ELEMENTS	Leaf	UINT8 or UINT16			TRUE

Define-Huffman-Tables Marker Segment Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"HuffmanTable"	ImGearJPEGTagIDs.HUFFMAN_TABLE	Tree

"HuffmanTable"	ImGearJPEGTagIDs.HUFFMAN_TABLE	Tree

Define-Huffman-Table Table Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"Descriptor"	ImGearJPEGTagIDs. HUFFMAN_TABLE_DESCRIPTOR	Leaf	UINT8			TRUE
"Lengths"	ImGearJPEGTagIDs. HUFFMAN_TABLE_LENGTH	Leaf	UINT8			TRUE
"Values"	ImGearJPEGTagIDs. HUFFMAN_TABLE_VALUES	Leaf	UINT8			TRUE

"Values"	ImGearJPEGTagIDs. HUFFMAN_TABLE_VALUES	Leaf	UINT8			TRUE

Comment Marker Segment Level

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"Comment"	ImGearJPEGTagIDs. COMMENT	Leaf	STRING		<ValueSize>	FALSE

Application Marker Segment Level

There are several application marker segments, which data structure is well known. These segments are parsed and their data are passed in special format.

These marker segments are:

See JFIF APP0 segment.
JFIF extension (JFXX) APP0 segment (read only)
EXIF APP1 segment
See Photoshop Image Resource APP13 marker segment. (it includes some IPTC data and another See Photoshop Image Resource metadata structure. )
See Other application marker segment levels.

JFIF APP0 Segment

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"JFIF_HEADER"	ImGearJPEGTagIDs. JFIF_ID	Leaf	STRING	JFIF	5	TRUE
"Version"	ImGearJPEGTagIDs. JFIF_VERSION	Leaf	UINT16		1	FALSE
"ResolutionUnits"	ImGearJPEGTagIDs. JFIF_UNITS	Leaf	UINT8		1	FALSE
"ResolutionX"	ImGearJPEGTagIDs. JFIF_X_RES	Leaf	UINT16		1	FALSE
"ResolutionY"	ImGearJPEGTagIDs. JFIF_Y_RES	Leaf	UINT16		1	FALSE
"ThumbnailWidth"18	ImGearJPEGTagIDs. JFIF_THUMB_WIDTH	Leaf	UINT8		1	TRUE
"ThumbnailHeight"19	ImGearJPEGTagIDs. JFIF_THUMB_HEIGHT	Leaf	UINT8		1	TRUE

Photoshop Image Resource APP13 Marker Segment

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"PHOTOSHOP_HEADER"	ImGearJPEGTagIDs. PHOTOSHOP_HEADER	Leaf	STRING	"Photoshop 3.0"	14	FALSE
Photoshop Image Resource level 1
...
Photoshop Image Resource level n

Note:: For "Photoshop Image Resource" metadata structure see Photoshop Image Resource metadata structure Table.

Other Application Marker Segment Levels

Name	Id	Type	Value Type	Value	Value Length	Ignored on save
"DATA"	ImGearJPEGTagIDs. BINARY_DATA	Leaf	RAW_DATA		<ValueSize>	FALSE