Detailed finishing TIFF image file format

1 What is TIFF?  
TIFF is an abbreviation of Tagged Image File Format. In today's standards, only TIFF exist, other formulation has been discarded no. As a markup language, TIFF and other file formats biggest difference is that in addition to image data, it can record an image of a lot of other information. It records the image data is also more flexible way, in theory, any other image formats can be used as a TIFF, TIFF embedded inside. Such as JPEG, Lossless JPEG, JPEG2000 arbitrary data width and the original uncompressed data can be easily embedded into TIFF go. Because of its scalability, TIFF has been widely used in the fields of digital influence, remote sensing, medicine and the like. TIFF file extension is .tif or .tiff

2 TIFF file structure 
TIFF file three key words are: image file header Image File Header (IFH), image file directory Image File Directory (IFD) and directory entries Directory Entry (DE ). Each image is 8-byte IFH beginning of this IFH points to the first IFD. IFD contains various information of the image, also it contains a pointer to the actual image data.

IFH configuration: 
Byte 0-1: flag byte order, or the value of II MM. Indicating little endian II, also known as little-endian. MM is the first byte large, has become big-endian.
Byte 2-3: TIFF flag, generally 42 is
Byte 4-7: a first IFD offset. Can be in any position, but must be at a word boundary, i.e. must be a multiple of 2.

IFD configuration (0 represents the start position of this IFD): 
Byte 0-1: This indicates how many IFD contains DE, is assumed that the number n
Byte 2- (n * 12 + 1 ): n th DE
byte (12 * n-2 +) - (n-12 + *. 5): the IFD of an offset, which is set to 0 if no

DE configuration (12 a Byte): 
Byte 0-1: uniquely identifies the TAG
Byte 2-3: data type.
Byte 4-7: Number. By this data type and number of TAG may determine the number of bytes occupied by storage needs
Byte 8-11: If the number of bytes occupied by less than 4, the data is stored directly thereto. If more than 4, where it is stored in a pointer to the actual data

A TIFF file may contain more IFD, each IFD is a subfolder. Baseline decoder as long as the first image data for solving a corresponding IFD. Extended TIFF images often contain multiple IFD, each IFD contains different information.

Below is a tif image W * H * 12 6 illustrate an example where RGB :( respectively 150,100,50)

0000-0007: header, it can be seen, which is a byte order II, the first IFD offset E6.

00E0-018D: first IFD. Directory Entry Count value of (00E0-00E1) is E, showing that there are IFD DE 14, DE occupies 12 bytes each, DE 14 occupy a total of 168 bytes, plus Directory Entry Count occupies 2 bytes, plus the Offset to 4 bytes next IFD occupied by the IFD occupy a total of 174 bytes, hexadecimal is converted to AE, so its data ends at 018D. Offset to the value of the next IFD (last 4 bytes) are 0, it denotes the entire image file only this one IFD.

00E2-00ED: wherein 00E2-00E3 is the first in the 1st IFD DE tag value 0100h, the representative image width; 00EA-00ED value 000Ch (12d) of the image width.

00EE-00F9: wherein 00EE-00EF IFD is the first in the second tag DE value 0101h, the representative image height; 00F6-00F9 image width value 0006h (6d).

011E-0129: 011E-011F of the tag value 0111H, representative of the offset of each Strip, 0126-0129 image data corresponding to the address 0008h.

0142-014D: amount of image data for 00D8h (216).

0008-00DF: image data.

reference:

[1] https://www.cnblogs.com/gywei/p/3393816.html

[2] https://blog.csdn.net/han_jiang_xue/article/details/8266207

[3] https://www.cnblogs.com/qiaozhoulin/p/4556207.html

 

Annex 1: TIFF 12 data types

1 = BYTE 8-bit unsigned integer.
2 = ASCII 8-bit byte that contains a 7-bit ASCII code; the last byte
must be NUL (binary zero).
3 = SHORT 16-bit (2-byte) unsigned integer.
4 = LONG 32-bit (4-byte) unsigned integer.
5 = RATIONAL Two LONGs: the first represents the numerator
6 = SBYTE An 8-bit signed (twos-complement) integer.
7 = UNDEFINED An 8-bit byte that may contain anything, depending on
the definition of the field.
8 = SSHORT A 16-bit (2-byte) signed (twos-complement) integer.
9 = SLONG A 32-bit (4-byte) signed (twos-complement) integer.
10 = SRATIONAL Two SLONG’s: the first represents the numerator of a
fraction, the second the denominator.
11 = FLOAT Single precision (4-byte) IEEE format.
12 = DOUBLE Double precision (8-byte) IEEE format.

 

Annex 2: Tiff Tag Reference ( https://www.awaresystems.be/imaging/tiff/tifftags/baseline.html )

Tag is all the basic TIFF codec must support Tag

code		name	Short description
Decimal code	Hex
254	00FE	NewSubfileType	New subfile type identifier length of LONG 1 With bits to identify the type of an image If Bit0 is 1 for thumbnails If Bit1 1 represents a multi-page image of a page Bit2 is 1 if it is representative of the transparency of the mask image The remaining bits being not defined. And SubfileType that this Tag bits used to distinguish a file type instead of the value to distinguish
255	00FF	SubfileType	SHORT subfile type identifier length 1 1 full resolution image 2 reduced resolution image Page 3 of a multi-page image Outdated Tag, is no longer used.
256	0100	ImageWidth	LONG or SHORT image width to length 1
257	0101	ImageLength	LONG or SHORT image height of length 1
258	0102	BitsPerSample	Bit number SHORT length of each component is SamplesPerPixel
259	0103	Compression	SHORT length compression type 1 With the continuous expansion TIFF, and currently supports up to dozens of compression. In my personal opinion, most need to focus on the following two values: Compression = 1: no compression Compression = 7: JPEG compression. If an RGB image and SamplesPerPixel = 3, then the lossy JPEG compression standard. If CFA image, it is Lossless JPEG
262	0106	PhotometricInterpretation	颜色空间 SHORT 长度为1   0 = WhiteIsZero. 应用于灰度或者二值图像， 0对应最亮灰度. 1 = BlackIsZero. 应用于灰度或者二值图像. 0对应最暗灰度。 2 = RGB. 正常RGB图像，存储顺序为R，G，B. 3 = Palette color. 索引图像, ColorMap必须定义，SamplesPerPixel必须1. 32803 = CFA (Color Filter Array)
263	0107	Threshholding	定义了转换成二值图像的阈值，忽略之
264	0108	CellWidth	The width of the dithering or halftoning matrix used to create a dithered or halftoned bilevel file.
265	0109	CellLength	The length of the dithering or halftoning matrix used to create a dithered or halftoned bilevel file.
266	010A	FillOrder	在同一字节中的逻辑顺序。一般不做定义，要定义的话建议用1
270	010E	ImageDescription	字符串， 对图像的描述
271	010F	Make	字符串， 生产厂商的描述
272	0110	Model	字符串
273	0111	StripOffsets	每个Strip的偏移量 SHORT或者LONG N = StripsPerImage for PlanarConfiguration equal to 1; N = SamplesPerPixel * StripsPerImage for PlanarConfiguration equal to 2
274	0112	Orientation	The orientation of the image with respect to the rows and columns.
277	0115	SamplesPerPixel	每个象素的通道数 SHORT 长度为1
278	0116	RowsPerStrip	每个Strip有多少行 SHORT或者LONG 长度为1。Default是无限大 StripsPerImage = floor ((ImageLength + RowsPerStrip - 1) / RowsPerStrip).
279	0117	StripByteCounts	每个Strip的长度 SHORT或者LONG N = StripsPerImage for PlanarConfiguration equal to 1; N = SamplesPerPixel * StripsPerImage for PlanarConfiguration equal to 2
280	0118	MinSampleValue	The minimum component value used.
281	0119	MaxSampleValue	The maximum component value used.
282	011A	XResolution	The number of pixels per ResolutionUnit in the ImageWidth direction.
283	011B	YResolution	The number of pixels per ResolutionUnit in the ImageLength direction.
284	011C	PlanarConfiguration	How the components of each pixel are stored.
288	0120	FreeOffsets	For each string of contiguous unused bytes in a TIFF file, the byte offset of the string.
289	0121	FreeByteCounts	For each string of contiguous unused bytes in a TIFF file, the number of bytes in the string.
290	0122	GrayResponseUnit	The precision of the information contained in the GrayResponseCurve.
291	0123	GrayResponseCurve	For grayscale data, the optical density of each possible pixel value.
296	0128	ResolutionUnit	The unit of measurement for XResolution and YResolution.
305	0131	Software	Name and version number of the software package(s) used to create the image.
306	0132	DateTime	Date and time of image creation.
315	013B	Artist	Person who created the image.
316	013C	HostComputer	The computer and/or operating system in use at the time of image creation.
320	0140	ColorMap	调色板
338	0152	ExtraSamples	Description of extra components.
33432	8298	Copyright	Copyright notice.