Create Pyramid layers with the same compressed setting as the band for HFA

[Sam Gillingham]

Attached patch makes the Pyramid layers compressed if the source band is compressed. This is what Imagine does, and can make resulting files much smaller.

[Sam Gillingham]

Patch to hfaband.cpp to make pyramid layers compressed if band is compressed

[Sam Gillingham]

Updated against trunk

[Sam Gillingham]

Just updated the patch against trunk. Any feedback on this ticket?

[Even Rouault]

I'm wondering if we shouldn't look at a HFA_COMPRESS_OVR configuration option first. If not defined, then take the compression mode from the full resolution image like your proposed patch.

The advantage of the configuration option is that it can also be used when building .aux external overviews for other formats.

e.g: gdaladdo out.tif --config USE_RRD YES 2 --config HFA_COMPRESS_OVR YES

Modified patch :

Index: frmts/hfa/hfaband.cpp
===================================================================
--- frmts/hfa/hfaband.cpp	(révision 26132)
+++ frmts/hfa/hfaband.cpp	(copie de travail)
@@ -2059,12 +2059,29 @@
     }
 
 /* -------------------------------------------------------------------- */
+/*      Are we compressed? If so, overview should be too (unless        */
+/*      HFA_COMPRESS_OVR is defined).                                   */
+/*      Check RasterDMS like HFAGetBandInfo                             */
+/* -------------------------------------------------------------------- */
+    int bCompressionType = FALSE;
+    const char* pszCompressOvr = CPLGetConfigOption("HFA_COMPRESS_OVR", NULL);
+    if( pszCompressOvr != NULL )
+        bCompressionType = CSLTestBoolean(pszCompressOvr);
+    else
+    {
+        HFAEntry *poDMS = poNode->GetNamedChild( "RasterDMS" );
+
+        if( poDMS != NULL )
+            bCompressionType = poDMS->GetIntField( "compressionType" ) != 0;
+    }
+
+/* -------------------------------------------------------------------- */
 /*      Create the layer.                                               */
 /* -------------------------------------------------------------------- */
     osLayerName.Printf( "_ss_%d_", nOverviewLevel );
 
     if( !HFACreateLayer( psRRDInfo, poParent, osLayerName, 
-                         TRUE, 64, FALSE, bCreateLargeRaster, FALSE,
+                         TRUE, 64, bCompressionType, bCreateLargeRaster, FALSE,
                          nOXSize, nOYSize, nOverviewDataType, NULL,
                          nValidFlagsOffset, nDataOffset, 1, 0 ) )
         return -1;

What do you think of that ? It would be appropriate too to modify the frmt_hfa.html file to document the above behaviour.

[Sam Gillingham]

Sounds like an excellent idea to me! It definitely would be useful to be able to compress .aux overviews also.

[Sam Gillingham]

Have attached patch for frmt_hfa.html. Let me know if any other work is required to have this change accepted.

[Even Rouault]

There's an error in the doc patch. HFA_COMPRESS_OVR is a configuration option (i.e. something you can define with --config HFA_COMPRESS_OVR YES on a GDAL command line, or through an environmenet variable), and not a creation option of the driver (i.e. something you pass with -co NAME=VALUE)

[Sam Gillingham]

Patch to document behaviour of HFA_COMPRESS_OVR config option in frmt_hfa.html

[Sam Gillingham]

Doc patch updated.

[Even Rouault]

Pushed in r26190.