fix jpeg tiff pyramid save

we were not copying the quant tables on lower pyr levels correctly

add a test too

ChangeLog

@@ -5,6 +5,7 @@
 - command-line programs set glib prgname (no longer set for you by VIPS_INIT)
 - enable strip chopping for TIFF read [DavidStorm]
 - disable modules by default for static builds [kleisauke]
+- fix jpeg tiff pyramid save
 
 14/8/20 started 8.11
 - add vips_jpegload_source() and vips_svgload_source() to public C API

libvips/foreign/vips2tiff.c

@@ -2029,13 +2029,18 @@ wtiff_copy_tiff( Wtiff *wtiff, TIFF *out, TIFF *in )
 	for( tile_no = 0; tile_no < n; tile_no++ ) {
 		tsize_t len;
 
-		len = TIFFReadRawTile( in, tile_no, 
-			wtiff->compressed_buf, wtiff->compressed_buf_length );
-		if( len <= 0 ||
-			TIFFWriteRawTile( out, tile_no, 
-				wtiff->compressed_buf, len ) < 0 )
+                /* TIFFReadRawTile()/TIFFWriteRawTile() would save us
+		 * decompress/recompress, but they won't work for
+		 * JPEG-compressed tiles since they won't copy the 
+		 * JPEG quant tables we need. 
+                 */
+                len = TIFFReadEncodedTile( in, tile_no, buf, -1 );
+                if( len < 0 ||
+                        TIFFWriteEncodedTile( out, tile_no, buf, len ) < 0 ) {
+                        g_free( buf );
 			return( -1 );
 		}
+	}
 	g_free( buf );
 
 	return( 0 );

test/test-suite/test_foreign.py

@@ -415,6 +415,12 @@ class TestForeign:
         im = pyvips.Image.new_from_file(TIF4_FILE)
         self.save_load_file(".tif", "[bitdepth=4]", im)
 
+        filename = temp_filename(self.tempdir, '.tif')
+        self.colour.write_to_file(filename, pyramid=True, compression="jpeg")
+        x = pyvips.Image.new_from_file(filename, page=2)
+        assert x.width == 72
+        assert abs(x.avg() - 117.3) < 1
+
         filename = temp_filename(self.tempdir, '.tif')
         x = pyvips.Image.new_from_file(TIF_FILE)
         x = x.copy()