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author | Wim <wim@42.be> | 2020-12-31 14:48:12 +0100 |
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committer | GitHub <noreply@github.com> | 2020-12-31 14:48:12 +0100 |
commit | 4f20ebead36876a88391bf033d1de3e4cf0228da (patch) | |
tree | 70b6fd79c6a5e00c958c29a7bd3926f074e76ba6 /vendor/golang.org/x/image/tiff/consts.go | |
parent | a9f89dbc645aafc68daa9fc8d589f55104b535c7 (diff) | |
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Update vendor for next release (#1343)
Diffstat (limited to 'vendor/golang.org/x/image/tiff/consts.go')
-rw-r--r-- | vendor/golang.org/x/image/tiff/consts.go | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/vendor/golang.org/x/image/tiff/consts.go b/vendor/golang.org/x/image/tiff/consts.go new file mode 100644 index 00000000..3e5f7f14 --- /dev/null +++ b/vendor/golang.org/x/image/tiff/consts.go @@ -0,0 +1,149 @@ +// Copyright 2011 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package tiff + +// A tiff image file contains one or more images. The metadata +// of each image is contained in an Image File Directory (IFD), +// which contains entries of 12 bytes each and is described +// on page 14-16 of the specification. An IFD entry consists of +// +// - a tag, which describes the signification of the entry, +// - the data type and length of the entry, +// - the data itself or a pointer to it if it is more than 4 bytes. +// +// The presence of a length means that each IFD is effectively an array. + +const ( + leHeader = "II\x2A\x00" // Header for little-endian files. + beHeader = "MM\x00\x2A" // Header for big-endian files. + + ifdLen = 12 // Length of an IFD entry in bytes. +) + +// Data types (p. 14-16 of the spec). +const ( + dtByte = 1 + dtASCII = 2 + dtShort = 3 + dtLong = 4 + dtRational = 5 +) + +// The length of one instance of each data type in bytes. +var lengths = [...]uint32{0, 1, 1, 2, 4, 8} + +// Tags (see p. 28-41 of the spec). +const ( + tImageWidth = 256 + tImageLength = 257 + tBitsPerSample = 258 + tCompression = 259 + tPhotometricInterpretation = 262 + + tFillOrder = 266 + + tStripOffsets = 273 + tSamplesPerPixel = 277 + tRowsPerStrip = 278 + tStripByteCounts = 279 + + tT4Options = 292 // CCITT Group 3 options, a set of 32 flag bits. + tT6Options = 293 // CCITT Group 4 options, a set of 32 flag bits. + + tTileWidth = 322 + tTileLength = 323 + tTileOffsets = 324 + tTileByteCounts = 325 + + tXResolution = 282 + tYResolution = 283 + tResolutionUnit = 296 + + tPredictor = 317 + tColorMap = 320 + tExtraSamples = 338 + tSampleFormat = 339 +) + +// Compression types (defined in various places in the spec and supplements). +const ( + cNone = 1 + cCCITT = 2 + cG3 = 3 // Group 3 Fax. + cG4 = 4 // Group 4 Fax. + cLZW = 5 + cJPEGOld = 6 // Superseded by cJPEG. + cJPEG = 7 + cDeflate = 8 // zlib compression. + cPackBits = 32773 + cDeflateOld = 32946 // Superseded by cDeflate. +) + +// Photometric interpretation values (see p. 37 of the spec). +const ( + pWhiteIsZero = 0 + pBlackIsZero = 1 + pRGB = 2 + pPaletted = 3 + pTransMask = 4 // transparency mask + pCMYK = 5 + pYCbCr = 6 + pCIELab = 8 +) + +// Values for the tPredictor tag (page 64-65 of the spec). +const ( + prNone = 1 + prHorizontal = 2 +) + +// Values for the tResolutionUnit tag (page 18). +const ( + resNone = 1 + resPerInch = 2 // Dots per inch. + resPerCM = 3 // Dots per centimeter. +) + +// imageMode represents the mode of the image. +type imageMode int + +const ( + mBilevel imageMode = iota + mPaletted + mGray + mGrayInvert + mRGB + mRGBA + mNRGBA + mCMYK +) + +// CompressionType describes the type of compression used in Options. +type CompressionType int + +// Constants for supported compression types. +const ( + Uncompressed CompressionType = iota + Deflate + LZW + CCITTGroup3 + CCITTGroup4 +) + +// specValue returns the compression type constant from the TIFF spec that +// is equivalent to c. +func (c CompressionType) specValue() uint32 { + switch c { + case LZW: + return cLZW + case Deflate: + return cDeflate + case CCITTGroup3: + return cG3 + case CCITTGroup4: + return cG4 + } + return cNone +} |