simplify construction of the recovery progress bar

Instead of six separate images for the left end, right end, and tiled
center portion of the full and empty progress bars, just use two
images:  a full bar and an empty bar.  Draw the left side of the full
bar and the right side of the empty one, moving the boundary rightward
to "fill" the bar.  This makes recovery trivially smaller, and allows
fancier images to be used as progress bars.

Support paletted PNG images as resources.
diff --git a/minui/resources.c b/minui/resources.c
index 7ecfeef..3d2c727 100644
--- a/minui/resources.c
+++ b/minui/resources.c
@@ -97,9 +97,10 @@
     int color_type = info_ptr->color_type;
     int bit_depth = info_ptr->bit_depth;
     int channels = info_ptr->channels;
-    if (bit_depth != 8 || (channels != 3 && channels != 4) ||
-        (color_type != PNG_COLOR_TYPE_RGB &&
-         color_type != PNG_COLOR_TYPE_RGBA)) {
+    if (!(bit_depth == 8 &&
+          ((channels == 3 && color_type == PNG_COLOR_TYPE_RGB) ||
+           (channels == 4 && color_type == PNG_COLOR_TYPE_RGBA) ||
+           (channels == 1 && color_type == PNG_COLOR_TYPE_PALETTE)))) {
         return -7;
         goto exit;
     }
@@ -118,6 +119,10 @@
     surface->format = (channels == 3) ?
             GGL_PIXEL_FORMAT_RGBX_8888 : GGL_PIXEL_FORMAT_RGBA_8888;
 
+    if (color_type == PNG_COLOR_TYPE_PALETTE) {
+      png_set_palette_to_rgb(png_ptr);
+    }
+
     int y;
     if (channels == 3) {
         for (y = 0; y < height; ++y) {
diff --git a/res/images/indeterminate1.png b/res/images/indeterminate1.png
index 264bf27..90cb9fb 100644
--- a/res/images/indeterminate1.png
+++ b/res/images/indeterminate1.png
Binary files differ
diff --git a/res/images/indeterminate2.png b/res/images/indeterminate2.png
index c30c049..f7fb289 100644
--- a/res/images/indeterminate2.png
+++ b/res/images/indeterminate2.png
Binary files differ
diff --git a/res/images/indeterminate3.png b/res/images/indeterminate3.png
index 891a000..ba10dfa 100644
--- a/res/images/indeterminate3.png
+++ b/res/images/indeterminate3.png
Binary files differ
diff --git a/res/images/indeterminate4.png b/res/images/indeterminate4.png
index 7a64151..ad5d9a5 100644
--- a/res/images/indeterminate4.png
+++ b/res/images/indeterminate4.png
Binary files differ
diff --git a/res/images/indeterminate5.png b/res/images/indeterminate5.png
index cd6ab20..8c19c8d 100644
--- a/res/images/indeterminate5.png
+++ b/res/images/indeterminate5.png
Binary files differ
diff --git a/res/images/indeterminate6.png b/res/images/indeterminate6.png
index ddd9e73..c0c6638 100644
--- a/res/images/indeterminate6.png
+++ b/res/images/indeterminate6.png
Binary files differ
diff --git a/res/images/progress_bar_empty.png b/res/images/progress_bar_empty.png
deleted file mode 100644
index 9013f04..0000000
--- a/res/images/progress_bar_empty.png
+++ /dev/null
Binary files differ
diff --git a/res/images/progress_bar_empty_left_round.png b/res/images/progress_bar_empty_left_round.png
deleted file mode 100644
index dae7d5d..0000000
--- a/res/images/progress_bar_empty_left_round.png
+++ /dev/null
Binary files differ
diff --git a/res/images/progress_bar_empty_right_round.png b/res/images/progress_bar_empty_right_round.png
deleted file mode 100644
index 5427088..0000000
--- a/res/images/progress_bar_empty_right_round.png
+++ /dev/null
Binary files differ
diff --git a/res/images/progress_bar_fill.png b/res/images/progress_bar_fill.png
deleted file mode 100644
index 37c04b4..0000000
--- a/res/images/progress_bar_fill.png
+++ /dev/null
Binary files differ
diff --git a/res/images/progress_bar_left_round.png b/res/images/progress_bar_left_round.png
deleted file mode 100644
index e72af47..0000000
--- a/res/images/progress_bar_left_round.png
+++ /dev/null
Binary files differ
diff --git a/res/images/progress_bar_right_round.png b/res/images/progress_bar_right_round.png
deleted file mode 100644
index d04c980..0000000
--- a/res/images/progress_bar_right_round.png
+++ /dev/null
Binary files differ
diff --git a/res/images/progress_empty.png b/res/images/progress_empty.png
new file mode 100644
index 0000000..4cb4998
--- /dev/null
+++ b/res/images/progress_empty.png
Binary files differ
diff --git a/res/images/progress_fill.png b/res/images/progress_fill.png
new file mode 100644
index 0000000..eb71754
--- /dev/null
+++ b/res/images/progress_fill.png
Binary files differ
diff --git a/ui.c b/ui.c
index 51df1fa..fdc0991 100644
--- a/ui.c
+++ b/ui.c
@@ -38,13 +38,11 @@
 #define PROGRESSBAR_INDETERMINATE_STATES 6
 #define PROGRESSBAR_INDETERMINATE_FPS 15
 
-enum { LEFT_SIDE, CENTER_TILE, RIGHT_SIDE, NUM_SIDES };
-
 static pthread_mutex_t gUpdateMutex = PTHREAD_MUTEX_INITIALIZER;
 static gr_surface gBackgroundIcon[NUM_BACKGROUND_ICONS];
 static gr_surface gProgressBarIndeterminate[PROGRESSBAR_INDETERMINATE_STATES];
-static gr_surface gProgressBarEmpty[NUM_SIDES];
-static gr_surface gProgressBarFill[NUM_SIDES];
+static gr_surface gProgressBarEmpty;
+static gr_surface gProgressBarFill;
 
 static const struct { gr_surface* surface; const char *name; } BITMAPS[] = {
     { &gBackgroundIcon[BACKGROUND_ICON_INSTALLING], "icon_installing" },
@@ -59,12 +57,8 @@
     { &gProgressBarIndeterminate[3],    "indeterminate4" },
     { &gProgressBarIndeterminate[4],    "indeterminate5" },
     { &gProgressBarIndeterminate[5],    "indeterminate6" },
-    { &gProgressBarEmpty[LEFT_SIDE],    "progress_bar_empty_left_round" },
-    { &gProgressBarEmpty[CENTER_TILE],  "progress_bar_empty" },
-    { &gProgressBarEmpty[RIGHT_SIDE],   "progress_bar_empty_right_round" },
-    { &gProgressBarFill[LEFT_SIDE],     "progress_bar_left_round" },
-    { &gProgressBarFill[CENTER_TILE],   "progress_bar_fill" },
-    { &gProgressBarFill[RIGHT_SIDE],    "progress_bar_right_round" },
+    { &gProgressBarEmpty,               "progress_empty" },
+    { &gProgressBarFill,                "progress_fill" },
     { NULL,                             NULL },
 };
 
@@ -123,8 +117,8 @@
     if (gProgressBarType == PROGRESSBAR_TYPE_NONE) return;
 
     int iconHeight = gr_get_height(gBackgroundIcon[BACKGROUND_ICON_INSTALLING]);
-    int width = gr_get_width(gProgressBarIndeterminate[0]);
-    int height = gr_get_height(gProgressBarIndeterminate[0]);
+    int width = gr_get_width(gProgressBarEmpty);
+    int height = gr_get_height(gProgressBarEmpty);
 
     int dx = (gr_fb_width() - width)/2;
     int dy = (3*gr_fb_height() + iconHeight - 2*height)/4;
@@ -137,18 +131,12 @@
         float progress = gProgressScopeStart + gProgress * gProgressScopeSize;
         int pos = (int) (progress * width);
 
-        gr_surface s = (pos ? gProgressBarFill : gProgressBarEmpty)[LEFT_SIDE];
-        gr_blit(s, 0, 0, gr_get_width(s), gr_get_height(s), dx, dy);
-
-        int x = gr_get_width(s);
-        while (x + (int) gr_get_width(gProgressBarEmpty[RIGHT_SIDE]) < width) {
-            s = (pos > x ? gProgressBarFill : gProgressBarEmpty)[CENTER_TILE];
-            gr_blit(s, 0, 0, gr_get_width(s), gr_get_height(s), dx + x, dy);
-            x += gr_get_width(s);
+        if (pos > 0) {
+          gr_blit(gProgressBarFill, 0, 0, pos, height, dx, dy);
         }
-
-        s = (pos > x ? gProgressBarFill : gProgressBarEmpty)[RIGHT_SIDE];
-        gr_blit(s, 0, 0, gr_get_width(s), gr_get_height(s), dx + x, dy);
+        if (pos < width-1) {
+          gr_blit(gProgressBarEmpty, pos, 0, width-pos, height, dx+pos, dy);
+        }
     }
 
     if (gProgressBarType == PROGRESSBAR_TYPE_INDETERMINATE) {