Fix loading of RLE bitmaps in wxBMPHandler

- Fix handling of delta encoding that change vertical position
- Fix handling of end-of-line encodings that are given mid-line
- Removed unnecessary computation for linepos

Add regression tests for the bitmaps using RLE and loading which
previously didn't work correctly.

Closes https://github.com/wxWidgets/wxWidgets/pull/2590

Closes #19318.

build/cmake/tests/gui/CMakeLists.txt

@@ -146,6 +146,9 @@ set(TEST_GUI_DATA
     horse.xpm
     image/8bpp-colorsused-large.bmp
     image/8bpp-colorsused-negative.bmp
+    image/rle4-delta-320x240.bmp
+    image/rle8-delta-320x240-expected.bmp
+    image/rle8-delta-320x240.bmp
     image/horse_grey.bmp
     image/horse_grey_flipped.bmp
     image/horse_rle4.bmp

src/common/imagbmp.cpp

@@ -772,11 +772,15 @@ bool wxBMPHandler::DoLoadDib(wxImage * image, int width, int height,
 
                         if ( first == 0 )
                         {
+                            // This is an escape sequence with special meaning.
                             if ( aByte == 0 )
                             {
                                 // end of scanline marker
+                                // This is ignored if the end-of-line was
+                                // implicitly assumed when column==width,
+                                // in which case column is now 0.
+                                if (column != 0)
                                     column = width;
-                                row--;
                             }
                             else if ( aByte == 1 )
                             {
@@ -787,18 +791,23 @@ bool wxBMPHandler::DoLoadDib(wxImage * image, int width, int height,
                             else if ( aByte == 2 )
                             {
                                 // delta marker, move in image
+
+                                // process column offset
                                 aByte = stream.GetC();
                                 if ( !stream.IsOk() )
                                     return false;
                                 column += aByte;
-                                linepos = column * bpp / 4;
+
+                                // process row offset
                                 aByte = stream.GetC();
                                 if ( !stream.IsOk() )
                                     return false;
-                                row += aByte; // upside down
+                                row += aByte;
+                                line = isUpsideDown ? height - 1 - row : row;
                             }
                             else
                             {
+                                // absolute mode (pixels not runs)
                                 int absolute = aByte;
                                 wxUint8 nibble[2] ;
                                 int readBytes = 0 ;
@@ -817,8 +826,6 @@ bool wxBMPHandler::DoLoadDib(wxImage * image, int width, int height,
                                     ptr[poffset + 1] = cmap[nibble[k%2]].g;
                                     ptr[poffset + 2] = cmap[nibble[k%2]].b;
                                     column++;
-                                    if ( k % 2 )
-                                        linepos++;
                                 }
                                 if ( readBytes & 0x01 )
                                 {
@@ -840,8 +847,6 @@ bool wxBMPHandler::DoLoadDib(wxImage * image, int width, int height,
                                 ptr[poffset + 1] = cmap[nibble[l%2]].g;
                                 ptr[poffset + 2] = cmap[nibble[l%2]].b;
                                 column++;
-                                if ( l % 2 )
-                                    linepos++;
                             }
                         }
                     }
@@ -874,8 +879,11 @@ bool wxBMPHandler::DoLoadDib(wxImage * image, int width, int height,
                             if ( aByte == 0 )
                             {
                                 // end of scanline marker
+                                // This is ignored if the end-of-line was
+                                // implicitly assumed when column==width,
+                                // in which case column is now 0.
+                                if (column != 0)
                                     column = width;
-                                row--;
                             }
                             else if ( aByte == 1 )
                             {
@@ -886,22 +894,26 @@ bool wxBMPHandler::DoLoadDib(wxImage * image, int width, int height,
                             else if ( aByte == 2 )
                             {
                                 // delta marker, move in image
+
+                                // process column offset
                                 aByte = stream.GetC();
                                 if ( !stream.IsOk() )
                                     return false;
                                 column += aByte;
-                                linepos = column * bpp / 8;
+
+                                // process row offset
                                 aByte = stream.GetC();
                                 if ( !stream.IsOk() )
                                     return false;
-                                row -= aByte;
+                                row += aByte;
+                                line = isUpsideDown ? height - 1 - row : row;
                             }
                             else
                             {
+                                // absolute mode (pixels not runs)
                                 int absolute = aByte;
                                 for (int k = 0; k < absolute; k++)
                                 {
-                                    linepos++;
                                     aByte = stream.GetC();
                                     if ( !stream.IsOk() )
                                         return false;
@@ -920,13 +932,13 @@ bool wxBMPHandler::DoLoadDib(wxImage * image, int width, int height,
                         }
                         else
                         {
+                            // encoded mode (repeat aByte first times)
                             for ( int l = 0; l < first && column < width; l++ )
                             {
                                 ptr[poffset    ] = cmap[aByte].r;
                                 ptr[poffset + 1] = cmap[aByte].g;
                                 ptr[poffset + 2] = cmap[aByte].b;
                                 column++;
-                                linepos++;
                             }
                         }
                     }
@@ -994,7 +1006,7 @@ bool wxBMPHandler::DoLoadDib(wxImage * image, int width, int height,
                 column++;
             }
         }
-        while ( (linepos < linesize) && (comp != 1) && (comp != 2) )
+        while ( (linepos < linesize) && (comp != BI_RLE8) && (comp != BI_RLE4) )
         {
             ++linepos;
             if ( !stream.ReadAll(&aByte, 1) )

tests/Makefile.in

@@ -565,7 +565,7 @@ data:
 
 data-images: 
 	@mkdir -p image
-	@for f in 8bpp-colorsused-large.bmp 8bpp-colorsused-negative.bmp horse_grey.bmp horse_grey_flipped.bmp horse_rle4.bmp horse_rle4_flipped.bmp horse_rle8.bmp horse_rle8_flipped.bmp horse_bicubic_50x50.png horse_bicubic_100x100.png horse_bicubic_150x150.png horse_bicubic_300x300.png horse_bilinear_50x50.png horse_bilinear_100x100.png horse_bilinear_150x150.png horse_bilinear_300x300.png horse_box_average_50x50.png horse_box_average_100x100.png horse_box_average_150x150.png horse_box_average_300x300.png cross_bicubic_256x256.png cross_bilinear_256x256.png cross_box_average_256x256.png cross_nearest_neighb_256x256.png paste_input_background.png paste_input_black.png paste_input_overlay_transparent_border_opaque_square.png paste_input_overlay_transparent_border_semitransparent_circle.png paste_input_overlay_transparent_border_semitransparent_square.png paste_result_background_plus_circle_plus_square.png paste_result_background_plus_overlay_transparent_border_opaque_square.png paste_result_background_plus_overlay_transparent_border_semitransparent_square.png paste_result_no_background_square_over_circle.png wx.png wx.ico toucan.png toucan_hue_0.538.png toucan_sat_-0.41.png toucan_bright_-0.259.png toucan_hsv_0.538_-0.41_-0.259.png toucan_light_46.png toucan_dis_240.png toucan_grey.png toucan_mono_255_255_255.png; do \
+	@for f in 8bpp-colorsused-large.bmp 8bpp-colorsused-negative.bmp rle4-delta-320x240.bmp rle8-delta-320x240.bmp rle8-delta-320x240-expected.bmp horse_grey.bmp horse_grey_flipped.bmp horse_rle4.bmp horse_rle4_flipped.bmp horse_rle8.bmp horse_rle8_flipped.bmp horse_bicubic_50x50.png horse_bicubic_100x100.png horse_bicubic_150x150.png horse_bicubic_300x300.png horse_bilinear_50x50.png horse_bilinear_100x100.png horse_bilinear_150x150.png horse_bilinear_300x300.png horse_box_average_50x50.png horse_box_average_100x100.png horse_box_average_150x150.png horse_box_average_300x300.png cross_bicubic_256x256.png cross_bilinear_256x256.png cross_box_average_256x256.png cross_nearest_neighb_256x256.png paste_input_background.png paste_input_black.png paste_input_overlay_transparent_border_opaque_square.png paste_input_overlay_transparent_border_semitransparent_circle.png paste_input_overlay_transparent_border_semitransparent_square.png paste_result_background_plus_circle_plus_square.png paste_result_background_plus_overlay_transparent_border_opaque_square.png paste_result_background_plus_overlay_transparent_border_semitransparent_square.png paste_result_no_background_square_over_circle.png wx.png wx.ico toucan.png toucan_hue_0.538.png toucan_sat_-0.41.png toucan_bright_-0.259.png toucan_hsv_0.538_-0.41_-0.259.png toucan_light_46.png toucan_dis_240.png toucan_grey.png toucan_mono_255_255_255.png; do \
 	if test ! -f image/$$f -a ! -d image/$$f ; \
 	then x=yep ; \
 	else x=`find $(srcdir)/image/$$f -newer image/$$f -print` ; \

tests/image/image.cpp

@@ -1355,6 +1355,11 @@ void ImageTestCase::BMPFlippingAndRLECompression()
     CompareBMPImage("image/horse_rle8.bmp", "image/horse_rle8_flipped.bmp");
 
     CompareBMPImage("image/horse_rle4.bmp", "image/horse_rle4_flipped.bmp");
+
+    CompareBMPImage("image/rle8-delta-320x240.bmp",
+                    "image/rle8-delta-320x240-expected.bmp");
+    CompareBMPImage("image/rle4-delta-320x240.bmp",
+                    "image/rle8-delta-320x240-expected.bmp");
 }
 
 

tests/makefile.gcc

@@ -555,7 +555,7 @@ data:
 
 data-images: 
 	if not exist image mkdir image
-	for %%f in (8bpp-colorsused-large.bmp 8bpp-colorsused-negative.bmp horse_grey.bmp horse_grey_flipped.bmp horse_rle4.bmp horse_rle4_flipped.bmp horse_rle8.bmp horse_rle8_flipped.bmp horse_bicubic_50x50.png horse_bicubic_100x100.png horse_bicubic_150x150.png horse_bicubic_300x300.png horse_bilinear_50x50.png horse_bilinear_100x100.png horse_bilinear_150x150.png horse_bilinear_300x300.png horse_box_average_50x50.png horse_box_average_100x100.png horse_box_average_150x150.png horse_box_average_300x300.png cross_bicubic_256x256.png cross_bilinear_256x256.png cross_box_average_256x256.png cross_nearest_neighb_256x256.png paste_input_background.png paste_input_black.png paste_input_overlay_transparent_border_opaque_square.png paste_input_overlay_transparent_border_semitransparent_circle.png paste_input_overlay_transparent_border_semitransparent_square.png paste_result_background_plus_circle_plus_square.png paste_result_background_plus_overlay_transparent_border_opaque_square.png paste_result_background_plus_overlay_transparent_border_semitransparent_square.png paste_result_no_background_square_over_circle.png wx.png wx.ico toucan.png toucan_hue_0.538.png toucan_sat_-0.41.png toucan_bright_-0.259.png toucan_hsv_0.538_-0.41_-0.259.png toucan_light_46.png toucan_dis_240.png toucan_grey.png toucan_mono_255_255_255.png) do if not exist image\%%f copy .\image\%%f image
+	for %%f in (8bpp-colorsused-large.bmp 8bpp-colorsused-negative.bmp rle4-delta-320x240.bmp rle8-delta-320x240.bmp rle8-delta-320x240-expected.bmp horse_grey.bmp horse_grey_flipped.bmp horse_rle4.bmp horse_rle4_flipped.bmp horse_rle8.bmp horse_rle8_flipped.bmp horse_bicubic_50x50.png horse_bicubic_100x100.png horse_bicubic_150x150.png horse_bicubic_300x300.png horse_bilinear_50x50.png horse_bilinear_100x100.png horse_bilinear_150x150.png horse_bilinear_300x300.png horse_box_average_50x50.png horse_box_average_100x100.png horse_box_average_150x150.png horse_box_average_300x300.png cross_bicubic_256x256.png cross_bilinear_256x256.png cross_box_average_256x256.png cross_nearest_neighb_256x256.png paste_input_background.png paste_input_black.png paste_input_overlay_transparent_border_opaque_square.png paste_input_overlay_transparent_border_semitransparent_circle.png paste_input_overlay_transparent_border_semitransparent_square.png paste_result_background_plus_circle_plus_square.png paste_result_background_plus_overlay_transparent_border_opaque_square.png paste_result_background_plus_overlay_transparent_border_semitransparent_square.png paste_result_no_background_square_over_circle.png wx.png wx.ico toucan.png toucan_hue_0.538.png toucan_sat_-0.41.png toucan_bright_-0.259.png toucan_hsv_0.538_-0.41_-0.259.png toucan_light_46.png toucan_dis_240.png toucan_grey.png toucan_mono_255_255_255.png) do if not exist image\%%f copy .\image\%%f image
 
 fr: 
 	if not exist $(OBJS)\intl\fr mkdir $(OBJS)\intl\fr

tests/makefile.vc

@@ -989,7 +989,7 @@ data:
 
 data-images: 
 	if not exist image mkdir image
-	for %f in (8bpp-colorsused-large.bmp 8bpp-colorsused-negative.bmp horse_grey.bmp horse_grey_flipped.bmp horse_rle4.bmp horse_rle4_flipped.bmp horse_rle8.bmp horse_rle8_flipped.bmp horse_bicubic_50x50.png horse_bicubic_100x100.png horse_bicubic_150x150.png horse_bicubic_300x300.png horse_bilinear_50x50.png horse_bilinear_100x100.png horse_bilinear_150x150.png horse_bilinear_300x300.png horse_box_average_50x50.png horse_box_average_100x100.png horse_box_average_150x150.png horse_box_average_300x300.png cross_bicubic_256x256.png cross_bilinear_256x256.png cross_box_average_256x256.png cross_nearest_neighb_256x256.png paste_input_background.png paste_input_black.png paste_input_overlay_transparent_border_opaque_square.png paste_input_overlay_transparent_border_semitransparent_circle.png paste_input_overlay_transparent_border_semitransparent_square.png paste_result_background_plus_circle_plus_square.png paste_result_background_plus_overlay_transparent_border_opaque_square.png paste_result_background_plus_overlay_transparent_border_semitransparent_square.png paste_result_no_background_square_over_circle.png wx.png wx.ico toucan.png toucan_hue_0.538.png toucan_sat_-0.41.png toucan_bright_-0.259.png toucan_hsv_0.538_-0.41_-0.259.png toucan_light_46.png toucan_dis_240.png toucan_grey.png toucan_mono_255_255_255.png) do if not exist image\%f copy .\image\%f image
+	for %f in (8bpp-colorsused-large.bmp 8bpp-colorsused-negative.bmp rle4-delta-320x240.bmp rle8-delta-320x240.bmp rle8-delta-320x240-expected.bmp horse_grey.bmp horse_grey_flipped.bmp horse_rle4.bmp horse_rle4_flipped.bmp horse_rle8.bmp horse_rle8_flipped.bmp horse_bicubic_50x50.png horse_bicubic_100x100.png horse_bicubic_150x150.png horse_bicubic_300x300.png horse_bilinear_50x50.png horse_bilinear_100x100.png horse_bilinear_150x150.png horse_bilinear_300x300.png horse_box_average_50x50.png horse_box_average_100x100.png horse_box_average_150x150.png horse_box_average_300x300.png cross_bicubic_256x256.png cross_bilinear_256x256.png cross_box_average_256x256.png cross_nearest_neighb_256x256.png paste_input_background.png paste_input_black.png paste_input_overlay_transparent_border_opaque_square.png paste_input_overlay_transparent_border_semitransparent_circle.png paste_input_overlay_transparent_border_semitransparent_square.png paste_result_background_plus_circle_plus_square.png paste_result_background_plus_overlay_transparent_border_opaque_square.png paste_result_background_plus_overlay_transparent_border_semitransparent_square.png paste_result_no_background_square_over_circle.png wx.png wx.ico toucan.png toucan_hue_0.538.png toucan_sat_-0.41.png toucan_bright_-0.259.png toucan_hsv_0.538_-0.41_-0.259.png toucan_light_46.png toucan_dis_240.png toucan_grey.png toucan_mono_255_255_255.png) do if not exist image\%f copy .\image\%f image
 
 fr: 
 	if not exist $(OBJS)\intl\fr mkdir $(OBJS)\intl\fr

tests/test.bkl

@@ -351,6 +351,9 @@
         <files>
             8bpp-colorsused-large.bmp
             8bpp-colorsused-negative.bmp
+            rle4-delta-320x240.bmp
+            rle8-delta-320x240.bmp
+            rle8-delta-320x240-expected.bmp
 
             horse_grey.bmp horse_grey_flipped.bmp
             horse_rle4.bmp horse_rle4_flipped.bmp