func (c CompressionType) specValue() uint32 {
	switch c {
	case Deflate:
		return cDeflate
	}
	return cNone
}
specValue returns the compression type constant from the TIFF spec that
is equivalent to c.
package tiff
const (
	leHeader = "II\x2A\x00"  
	beHeader = "MM\x00\x2A"  
	ifdLen = 12  
)
const (
	dtByte     = 1
	dtASCII    = 2
	dtShort    = 3
	dtLong     = 4
	dtRational = 5
)
var lengths = [...]uint32{0, 1, 1, 2, 4, 8}
const (
	tImageWidth                = 256
	tImageLength               = 257
	tBitsPerSample             = 258
	tCompression               = 259
	tPhotometricInterpretation = 262
	tStripOffsets    = 273
	tSamplesPerPixel = 277
	tRowsPerStrip    = 278
	tStripByteCounts = 279
	tTileWidth      = 322
	tTileLength     = 323
	tTileOffsets    = 324
	tTileByteCounts = 325
	tXResolution    = 282
	tYResolution    = 283
	tResolutionUnit = 296
	tPredictor    = 317
	tColorMap     = 320
	tExtraSamples = 338
	tSampleFormat = 339
)
const (
	cNone       = 1
	cCCITT      = 2
	cG3         = 3  
	cG4         = 4  
	cLZW        = 5
	cJPEGOld    = 6  
	cJPEG       = 7
	cDeflate    = 8  
	cPackBits   = 32773
	cDeflateOld = 32946  
)
const (
	pWhiteIsZero = 0
	pBlackIsZero = 1
	pRGB         = 2
	pPaletted    = 3
	pTransMask   = 4  
	pCMYK        = 5
	pYCbCr       = 6
	pCIELab      = 8
)
const (
	prNone       = 1
	prHorizontal = 2
)
const (
	resNone    = 1
	resPerInch = 2  
	resPerCM   = 3  
)
type imageMode int
const (
	mBilevel imageMode = iota
	mPaletted
	mGray
	mGrayInvert
	mRGB
	mRGBA
	mNRGBA
)
type CompressionType int
const (
	Uncompressed CompressionType = iota
	Deflate
)