[PATCH] 3/5 Bitmap scaling

[Colin D Bennett <colin@gibibit.com>]

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This patch adds bitmap scaling support to GRUB.

It also adds support to gfxterm for scaling the background image to fit
the screen.  The background_image command supports a new -m/--mode
option, which takes "stretch" (the default) or "normal" as values.

The patch is against GRUB trunk revision 1964.

Vesa started a discussion about more flexible handling of bitmaps
including the concept of optimizing loaded bitmaps into a
display-specific format, at which point they could no longer be
modified by functions like the bitmap scaling functions.

This bitmap format optimization would be nice to add, but I think we
can at least add this basic bitmap scaling functionality to start
with.  It only supports 24/32 bpp direct color modes at this point to
keep things simple.

Regards,
Colin

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=== modified file 'conf/common.rmk'
--- conf/common.rmk	2009-01-13 16:34:26 +0000
+++ conf/common.rmk	2009-01-31 20:28:20 +0000
@@ -446,7 +446,7 @@
 videotest_mod_LDFLAGS = $(COMMON_LDFLAGS)
 
 # For bitmap.mod
-bitmap_mod_SOURCES = video/bitmap.c
+bitmap_mod_SOURCES = video/bitmap.c video/bitmap_scale.c
 bitmap_mod_CFLAGS = $(COMMON_CFLAGS)
 bitmap_mod_LDFLAGS = $(COMMON_LDFLAGS)
 

=== added file 'include/grub/bitmap_scale.h'
--- include/grub/bitmap_scale.h	1970-01-01 00:00:00 +0000
+++ include/grub/bitmap_scale.h	2009-01-31 20:18:45 +0000
@@ -0,0 +1,48 @@
+/* bitmap_scale.h - Bitmap scaling functions. */
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2008,2009  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef GRUB_BITMAP_SCALE_HEADER
+#define GRUB_BITMAP_SCALE_HEADER 1
+
+#include <grub/err.h>
+#include <grub/types.h>
+#include <grub/bitmap_scale.h>
+
+enum grub_video_bitmap_scale_method
+{
+  /* Choose the fastest interpolation algorithm.  */
+  GRUB_VIDEO_BITMAP_SCALE_METHOD_FASTEST,
+  /* Choose the highest quality interpolation algorithm.  */
+  GRUB_VIDEO_BITMAP_SCALE_METHOD_BEST,
+
+  /* Specific algorithms:  */
+  /* Nearest neighbor interpolation.  */
+  GRUB_VIDEO_BITMAP_SCALE_METHOD_NEAREST,
+  /* Bilinear interpolation.  */
+  GRUB_VIDEO_BITMAP_SCALE_METHOD_BILINEAR
+};
+
+grub_err_t
+grub_video_bitmap_create_scaled (struct grub_video_bitmap **dst,
+                                 int dst_width, int dst_height,
+                                 struct grub_video_bitmap *src,
+                                 enum
+                                 grub_video_bitmap_scale_method scale_method);
+
+#endif /* ! GRUB_BITMAP_SCALE_HEADER */

=== modified file 'term/gfxterm.c'
--- term/gfxterm.c	2009-01-19 17:09:53 +0000
+++ term/gfxterm.c	2009-01-31 20:28:20 +0000
@@ -27,6 +27,7 @@
 #include <grub/env.h>
 #include <grub/video.h>
 #include <grub/bitmap.h>
+#include <grub/bitmap_scale.h>
 
 #define DEFAULT_VIDEO_WIDTH	640
 #define DEFAULT_VIDEO_HEIGHT	480
@@ -1095,8 +1096,18 @@
   dirty_region_redraw ();
 }
 
+
+/* Option array indices. */
+#define BACKGROUND_CMD_ARGINDEX_MODE 0
+
+static const struct grub_arg_option background_image_cmd_options[] = {
+  {"mode", 'm', 0, "Background image mode (`stretch', `normal').", 0, 
+    ARG_TYPE_STRING},
+  {0, 0, 0, 0, 0, 0}
+};
+
 static grub_err_t
-grub_gfxterm_background_image_cmd (struct grub_arg_list *state __attribute__ ((unused)),
+grub_gfxterm_background_image_cmd (struct grub_arg_list *state,
                                    int argc,
                                    char **args)
 {
@@ -1123,12 +1134,36 @@
     if (grub_errno != GRUB_ERR_NONE)
       return grub_errno;
 
+    /* Determine if the bitmap should be scaled to fit the screen. */
+    if (!state[BACKGROUND_CMD_ARGINDEX_MODE].set
+        || grub_strcmp (state[BACKGROUND_CMD_ARGINDEX_MODE].arg,
+                        "stretch") == 0)
+        {
+          if (mode_info.width != grub_video_bitmap_get_width (bitmap)
+              || mode_info.height != grub_video_bitmap_get_height (bitmap)) 
+            {
+              struct grub_video_bitmap *scaled_bitmap;
+              grub_video_bitmap_create_scaled (&scaled_bitmap,
+                                              mode_info.width, 
+                                              mode_info.height,
+                                              bitmap,
+                                              GRUB_VIDEO_BITMAP_SCALE_METHOD_BEST);
+              if (grub_errno == GRUB_ERR_NONE)
+                {
+                  /* Replace the original bitmap with the scaled one. */
+                  grub_video_bitmap_destroy (bitmap);
+                  bitmap = scaled_bitmap;
+                }
+            }
+        }
+
+
     /* If bitmap was loaded correctly, display it.  */
     if (bitmap)
       {
         /* Determine bitmap dimensions.  */
         bitmap_width = grub_video_bitmap_get_width (bitmap);
-        bitmap_height = grub_video_bitmap_get_width (bitmap);
+        bitmap_height = grub_video_bitmap_get_height (bitmap);
         
         /* Mark whole screen as dirty.  */
         dirty_region_reset ();
@@ -1171,7 +1206,7 @@
                          GRUB_COMMAND_FLAG_BOTH,
                          "background_image",
                          "Load background image for active terminal",
-                         0);
+                         background_image_cmd_options);
 }
 
 GRUB_MOD_FINI(term_gfxterm)

=== added file 'video/bitmap_scale.c'
--- video/bitmap_scale.c	1970-01-01 00:00:00 +0000
+++ video/bitmap_scale.c	2009-01-31 20:22:55 +0000
@@ -0,0 +1,307 @@
+/* bitmap_scale.c - Bitmap scaling. */
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2006,2007,2008,2009  Free Software Foundation, Inc.
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/mm.h>
+#include <grub/misc.h>
+#include <grub/video.h>
+#include <grub/bitmap.h>
+#include <grub/bitmap_scale.h>
+#include <grub/types.h>
+
+/* Prototypes for module-local functions.  */
+static grub_err_t scale_nn (struct grub_video_bitmap *dst,
+                            struct grub_video_bitmap *src);
+static grub_err_t scale_bilinear (struct grub_video_bitmap *dst,
+                                  struct grub_video_bitmap *src);
+
+/* This function creates a new scaled version of the bitmap SRC.  The new
+   bitmap has dimensions DST_WIDTH by DST_HEIGHT.  The scaling algorithm
+   is given by SCALE_METHOD.  If an error is encountered, the return code is
+   not equal to GRUB_ERR_NONE, and the bitmap DST is either not created, or
+   it is destroyed before this function returns.
+
+   Supports only direct color modes which have components separated
+   into bytes (e.g., RGBA 8:8:8:8 or BGR 8:8:8 true color).
+   But because of this simplifying assumption, the implementation is
+   greatly simplified.  */
+grub_err_t
+grub_video_bitmap_create_scaled (struct grub_video_bitmap **dst,
+                                 int dst_width, int dst_height,
+                                 struct grub_video_bitmap *src,
+                                 enum grub_video_bitmap_scale_method
+                                 scale_method)
+{
+  *dst = 0;
+
+  /* Verify the simplifying assumptions. */
+  if (src == 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT,
+                       "null src bitmap in grub_video_bitmap_create_scaled");
+  if (src->mode_info.red_field_pos % 8 != 0
+      || src->mode_info.green_field_pos % 8 != 0
+      || src->mode_info.blue_field_pos % 8 != 0
+      || src->mode_info.reserved_field_pos % 8 != 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT,
+                       "src format not supported for scale");
+  if (src->mode_info.width == 0 || src->mode_info.height == 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "bitmap has a zero dimension");
+  if (dst_width <= 0 || dst_height <= 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT,
+                       "requested to scale to a size w/ a zero dimension");
+  if (src->mode_info.bytes_per_pixel * 8 != src->mode_info.bpp)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT,
+                       "bitmap to scale has inconsistent Bpp and bpp");
+
+  /* Create the new bitmap. */
+  grub_err_t ret;
+  ret = grub_video_bitmap_create (dst, dst_width, dst_height,
+                                  src->mode_info.blit_format);
+  if (ret != GRUB_ERR_NONE)
+    return ret;                 /* Error. */
+
+  switch (scale_method)
+    {
+    case GRUB_VIDEO_BITMAP_SCALE_METHOD_FASTEST:
+    case GRUB_VIDEO_BITMAP_SCALE_METHOD_NEAREST:
+      ret = scale_nn (*dst, src);
+      break;
+    case GRUB_VIDEO_BITMAP_SCALE_METHOD_BEST:
+    case GRUB_VIDEO_BITMAP_SCALE_METHOD_BILINEAR:
+      ret = scale_bilinear (*dst, src);
+      break;
+    default:
+      ret = grub_error (GRUB_ERR_BAD_ARGUMENT, "Invalid scale_method value");
+      break;
+    }
+
+  if (ret == GRUB_ERR_NONE)
+    {
+      /* Success:  *dst is now a pointer to the scaled bitmap. */
+      return GRUB_ERR_NONE;
+    }
+  else
+    {
+      /* Destroy the bitmap and return the error code. */
+      grub_video_bitmap_destroy (*dst);
+      *dst = 0;
+      return ret;
+    }
+}
+
+/* Nearest neighbor bitmap scaling algorithm.
+
+   Copy the bitmap SRC to the bitmap DST, scaling the bitmap to fit the
+   dimensions of DST.  This function uses the nearest neighbor algorithm to
+   interpolate the pixels.
+
+   Supports only direct color modes which have components separated
+   into bytes (e.g., RGBA 8:8:8:8 or BGR 8:8:8 true color).
+   But because of this simplifying assumption, the implementation is
+   greatly simplified.  */
+static grub_err_t
+scale_nn (struct grub_video_bitmap *dst, struct grub_video_bitmap *src)
+{
+  /* Verify the simplifying assumptions. */
+  if (dst == 0 || src == 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "null bitmap in scale_nn");
+  if (dst->mode_info.red_field_pos % 8 != 0
+      || dst->mode_info.green_field_pos % 8 != 0
+      || dst->mode_info.blue_field_pos % 8 != 0
+      || dst->mode_info.reserved_field_pos % 8 != 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "dst format not supported");
+  if (src->mode_info.red_field_pos % 8 != 0
+      || src->mode_info.green_field_pos % 8 != 0
+      || src->mode_info.blue_field_pos % 8 != 0
+      || src->mode_info.reserved_field_pos % 8 != 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "src format not supported");
+  if (dst->mode_info.red_field_pos != src->mode_info.red_field_pos
+      || dst->mode_info.red_mask_size != src->mode_info.red_mask_size
+      || dst->mode_info.green_field_pos != src->mode_info.green_field_pos
+      || dst->mode_info.green_mask_size != src->mode_info.green_mask_size
+      || dst->mode_info.blue_field_pos != src->mode_info.blue_field_pos
+      || dst->mode_info.blue_mask_size != src->mode_info.blue_mask_size
+      || dst->mode_info.reserved_field_pos !=
+      src->mode_info.reserved_field_pos
+      || dst->mode_info.reserved_mask_size !=
+      src->mode_info.reserved_mask_size)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "dst and src not compatible");
+  if (dst->mode_info.bytes_per_pixel != src->mode_info.bytes_per_pixel)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "dst and src not compatible");
+  if (dst->mode_info.width == 0 || dst->mode_info.height == 0
+      || src->mode_info.width == 0 || src->mode_info.height == 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "bitmap has a zero dimension");
+
+  grub_uint8_t *ddata = dst->data;
+  grub_uint8_t *sdata = src->data;
+  int dw = dst->mode_info.width;
+  int dh = dst->mode_info.height;
+  int sw = src->mode_info.width;
+  int sh = src->mode_info.height;
+  int dstride = dst->mode_info.pitch;
+  int sstride = src->mode_info.pitch;
+  /* bytes_per_pixel is the same for both src and dst. */
+  int bytes_per_pixel = dst->mode_info.bytes_per_pixel;
+
+  int dy;
+  for (dy = 0; dy < dh; dy++)
+    {
+      int dx;
+      for (dx = 0; dx < dw; dx++)
+        {
+          grub_uint8_t *dptr;
+          grub_uint8_t *sptr;
+          int sx;
+          int sy;
+          int comp;
+
+          /* Compute the source coordinate that the destination coordinate
+             maps to.  Note: sx/sw = dx/dw  =>  sx = sw*dx/dw. */
+          sx = sw * dx / dw;
+          sy = sh * dy / dh;
+
+          /* Get the address of the pixels in src and dst. */
+          dptr = ddata + dy * dstride + dx * bytes_per_pixel;
+          sptr = sdata + sy * sstride + sx * bytes_per_pixel;
+
+          /* Copy the pixel color value. */
+          for (comp = 0; comp < bytes_per_pixel; comp++)
+            dptr[comp] = sptr[comp];
+        }
+    }
+  return GRUB_ERR_NONE;
+}
+
+/* Bilinear interpolation image scaling algorithm.
+
+   Copy the bitmap SRC to the bitmap DST, scaling the bitmap to fit the
+   dimensions of DST.  This function uses the bilinear interpolation algorithm
+   to interpolate the pixels.
+
+   Supports only direct color modes which have components separated
+   into bytes (e.g., RGBA 8:8:8:8 or BGR 8:8:8 true color).
+   But because of this simplifying assumption, the implementation is
+   greatly simplified.  */
+static grub_err_t
+scale_bilinear (struct grub_video_bitmap *dst, struct grub_video_bitmap *src)
+{
+  /* Verify the simplifying assumptions. */
+  if (dst == 0 || src == 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "null bitmap in scale func");
+  if (dst->mode_info.red_field_pos % 8 != 0
+      || dst->mode_info.green_field_pos % 8 != 0
+      || dst->mode_info.blue_field_pos % 8 != 0
+      || dst->mode_info.reserved_field_pos % 8 != 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "dst format not supported");
+  if (src->mode_info.red_field_pos % 8 != 0
+      || src->mode_info.green_field_pos % 8 != 0
+      || src->mode_info.blue_field_pos % 8 != 0
+      || src->mode_info.reserved_field_pos % 8 != 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "src format not supported");
+  if (dst->mode_info.red_field_pos != src->mode_info.red_field_pos
+      || dst->mode_info.red_mask_size != src->mode_info.red_mask_size
+      || dst->mode_info.green_field_pos != src->mode_info.green_field_pos
+      || dst->mode_info.green_mask_size != src->mode_info.green_mask_size
+      || dst->mode_info.blue_field_pos != src->mode_info.blue_field_pos
+      || dst->mode_info.blue_mask_size != src->mode_info.blue_mask_size
+      || dst->mode_info.reserved_field_pos !=
+      src->mode_info.reserved_field_pos
+      || dst->mode_info.reserved_mask_size !=
+      src->mode_info.reserved_mask_size)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "dst and src not compatible");
+  if (dst->mode_info.bytes_per_pixel != src->mode_info.bytes_per_pixel)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "dst and src not compatible");
+  if (dst->mode_info.width == 0 || dst->mode_info.height == 0
+      || src->mode_info.width == 0 || src->mode_info.height == 0)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, "bitmap has a zero dimension");
+
+  grub_uint8_t *ddata = dst->data;
+  grub_uint8_t *sdata = src->data;
+  int dw = dst->mode_info.width;
+  int dh = dst->mode_info.height;
+  int sw = src->mode_info.width;
+  int sh = src->mode_info.height;
+  int dstride = dst->mode_info.pitch;
+  int sstride = src->mode_info.pitch;
+  /* bytes_per_pixel is the same for both src and dst. */
+  int bytes_per_pixel = dst->mode_info.bytes_per_pixel;
+
+  int dy;
+  for (dy = 0; dy < dh; dy++)
+    {
+      int dx;
+      for (dx = 0; dx < dw; dx++)
+        {
+          grub_uint8_t *dptr;
+          grub_uint8_t *sptr;
+          int sx;
+          int sy;
+          int comp;
+
+          /* Compute the source coordinate that the destination coordinate
+             maps to.  Note: sx/sw = dx/dw  =>  sx = sw*dx/dw. */
+          sx = sw * dx / dw;
+          sy = sh * dy / dh;
+
+          /* Get the address of the pixels in src and dst. */
+          dptr = ddata + dy * dstride + dx * bytes_per_pixel;
+          sptr = sdata + sy * sstride + sx * bytes_per_pixel;
+
+          /* If we have enough space to do so, use bilinear interpolation.
+             Otherwise, fall back to nearest neighbor for this pixel. */
+          if (sx < sw - 1 && sy < sh - 1)
+            {
+              /* Do bilinear interpolation. */
+
+              /* Fixed-point .8 numbers representing the fraction of the
+                 distance in the x (u) and y (v) direction within the
+                 box of 4 pixels in the source. */
+              int u = (256 * sw * dx / dw) - (sx * 256);
+              int v = (256 * sh * dy / dh) - (sy * 256);
+
+              for (comp = 0; comp < bytes_per_pixel; comp++)
+                {
+                  /* Get the component's values for the
+                     four source corner pixels. */
+                  grub_uint8_t f00 = sptr[comp];
+                  grub_uint8_t f10 = sptr[comp + bytes_per_pixel];
+                  grub_uint8_t f01 = sptr[comp + sstride];
+                  grub_uint8_t f11 = sptr[comp + sstride + bytes_per_pixel];
+
+                  /* Do linear interpolations along the top and bottom
+                     rows of the box. */
+                  grub_uint8_t f0y = (256 - v) * f00 / 256 + v * f01 / 256;
+                  grub_uint8_t f1y = (256 - v) * f10 / 256 + v * f11 / 256;
+
+                  /* Interpolate vertically. */
+                  grub_uint8_t fxy = (256 - u) * f0y / 256 + u * f1y / 256;
+
+                  dptr[comp] = fxy;
+                }
+            }
+          else
+            {
+              /* Fall back to nearest neighbor interpolation. */
+              /* Copy the pixel color value. */
+              for (comp = 0; comp < bytes_per_pixel; comp++)
+                dptr[comp] = sptr[comp];
+            }
+        }
+    }
+  return GRUB_ERR_NONE;
+}


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