2006.03.30 10:21 "[Tiff] IJG in TIFF , control image qualit y by using quantity table in stead of jpe g_set_quality()", by Kelvin Zhong

Hi,All
  I want something like this:

1. set jpegtables tag in TIFF,using TIFFSetField(...)
2. IJG in TIFFLIB will using the jpegtables i set as quantity table to compression the image.
3. instead of call jpeg_set_quality() to set the quality and thus generate responding quantity
3. table.

Has anyone already done such a similiar things?

After i read the relative code of IJG,it seems we can do some work in these functions:

jpeg_set_linear_quality
jpeg_add_quant_table
jpeg_quality_scaling

If anyone happen to know ,pls send me some useful informations, include some sample code will be greatly appreciated.

thanks in advance.

Kingore@126.com

 From: "yourpattern"

Hi,All

 I want to use my own JPEG quality tables. not the standard tables it generated.
how should i do .for example .i have 2 tables.:

static BYTE JPEG_QT_CHR[64] = {
      12,      24,      24,      24,      27,      33,      39,      48,
      24,      24,      26,      30,      34,      40,      47,      55,
      24,      29,      34,      43,      52,      60,      69,      79,
      39,      41,      47,      56,      69,      84,     100,     116,
      57,      59,      65,      75,      90,     110,     134,     162,
      83,      85,      91,     103,     120,     144,     177,     218,
     119,     121,     129,     143,     164,     194,     236,     255,
     172,     175,     185,     203,     230,     255,     255,     255 };
static BYTE JPEG_QT_LUM[64] = {
      12,      17,      20,      33,      42,      53,      67,      86,
      17,      20,      33,      37,      45,      56,      71,      90,
      20,      33,      39,      46,      55,      67,      83,     103,
      33,      37,      46,      59,      72,      86,     103,     125,
      42,      45,      55,      72,      90,     110,     131,     157,
      53,      56,      67,      86,     110,     137,     167,     202,
      67,      71,      83,     103,     131,     167,     209,     255,
      86,      90,     103,     125,     157,     202,     255,     255 };

how can i do to make the jpeg compress process use these 2 tables ?

Do TIFFSetField(ptif, JPEGTABLES,...) works?

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