tiff density in 8bim

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bitozoid

tiff density in 8bim

Post by bitozoid »

I have found some problems when dealing with tiff density. I have a tiff file where tiff tags set units in cm, but 8bim profile is written in inches. Imagemagick loads tiff tags, and then modifies only the values but not the units when loading the 8bim profile.

In magick/profile.c, x_resolution and y_resolution is modified, but units are not:

Code: Select all

1554       case 0x03ed:
1555       {
1556         unsigned short
1557           resolution;
1558 
1559         /*
1560           Resolution.
1561         */
1562         p=ReadResourceShort(p,&resolution)+6;
1563         image->x_resolution=(double) resolution;
1564         p=ReadResourceShort(p,&resolution)+6;
1565         image->y_resolution=(double) resolution;
1566         break;
1567       }
Same code from gimp, in plug-ins/file-psd/psd-image-res-load.c:

Code: Select all

 491 static gint
 492 load_resource_1005 (const PSDimageres  *res_a,
 493                     const gint32        image_id,
 494                     FILE               *f,
 495                     GError            **error)
 496 {
 497   /* Load image resolution and unit of measure */
 498             
 499   /* FIXME  width unit and height unit unused at present */
 500       
 501   ResolutionInfo        res_info;
 502   GimpUnit              image_unit;
 503       
 504   IFDBG(2) g_debug ("Process image resource block 1005: Resolution Info");
 505     
 506   if (fread (&res_info.hRes, 4, 1, f) < 1
 507       || fread (&res_info.hResUnit, 2, 1, f) < 1
 508       || fread (&res_info.widthUnit, 2, 1, f) < 1
 509       || fread (&res_info.vRes, 4, 1, f) < 1
 510       || fread (&res_info.vResUnit, 2, 1, f) < 1
 511       || fread (&res_info.heightUnit, 2, 1, f) < 1)
 512     {
 513       psd_set_error (feof (f), errno, error);
 514       return -1;
 515     }
 516   res_info.hRes = GINT32_FROM_BE (res_info.hRes);
 517   res_info.hResUnit = GINT16_FROM_BE (res_info.hResUnit);
 518   res_info.widthUnit = GINT16_FROM_BE (res_info.widthUnit);
 519   res_info.vRes = GINT32_FROM_BE (res_info.vRes);
 520   res_info.vResUnit = GINT16_FROM_BE (res_info.vResUnit);
 521   res_info.heightUnit = GINT16_FROM_BE (res_info.heightUnit);
 522                       
 523   IFDBG(3) g_debug ("Resolution: %d, %d, %d, %d, %d, %d",
 524                       res_info.hRes,
 525                       res_info.hResUnit,
 526                       res_info.widthUnit,
 527                       res_info.vRes,
 528                       res_info.vResUnit,
 529                       res_info.heightUnit);
 530   
 531   /* Resolution always recorded as pixels / inch in a fixed point implied
 532      decimal int32 with 16 bits before point and 16 after (i.e. cast as
 533      double and divide resolution by 2^16 */
 534   gimp_image_set_resolution (image_id,
 535                              res_info.hRes / 65536.0, res_info.vRes / 65536.0);
 536       
 537   /* GIMP only has one display unit so use ps horizontal resolution unit */
 538   switch (res_info.hResUnit)
 539     { 
 540       case PSD_RES_INCH:
 541         image_unit = GIMP_UNIT_INCH;
 542         break;
 543       case PSD_RES_CM:
 544         image_unit = GIMP_UNIT_MM;
 545         break;
 546       default:
 547         image_unit = GIMP_UNIT_INCH;
 548     }
 549 
 550   gimp_image_set_unit (image_id, image_unit);
 551         
 552   return 0;
 553 }
Is this a bug or done on purpose?

See also http://answers.google.com/answers/threa ... 88091.html
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