Update image scaling subpixel offset calculations for top-down images.

3 files changed, 47 insertions, 45 deletions

diff --git a/draw/draw_device.c b/draw/draw_device.c
index 1cb3e4b9..12810420 100644
--- a/draw/draw_device.c
+++ b/draw/draw_device.c
@@ -504,7 +504,7 @@ fz_draw_fill_text(fz_device *devp, fz_text *text, fz_matrix ctm,
 			}
 			else
 			{
-				fz_matrix ctm = {glyph->w, 0.0, 0.0, -glyph->h, x + glyph->x, y + glyph->y + glyph->h};
+				fz_matrix ctm = {glyph->w, 0.0, 0.0, glyph->h, x + glyph->x, y + glyph->y};
 				fz_paint_image(state->dest, state->scissor, state->shape, glyph, ctm, alpha * 255);
 			}
 			fz_drop_pixmap(dev->ctx, glyph);
diff --git a/draw/draw_scale.c b/draw/draw_scale.c
index 65baee4f..b34f9770 100644
--- a/draw/draw_scale.c
+++ b/draw/draw_scale.c
@@ -1214,15 +1214,13 @@ fz_scale_pixmap(fz_context *ctx, fz_pixmap *src, float x, float y, float w, floa
 
 	/* Find the destination bbox, width/height, and sub pixel offset,
 	 * allowing for whether we're flipping or not. */
-	/* Note that the x and y sub pixel offsets here are different.
-	 * The (x,y) position given describes where the bottom left corner
-	 * of the source image should be mapped to (i.e. where (0,h) in image
-	 * space ends up, not the more logical and sane (0,0)). Also there
-	 * are differences in the way we scale horizontally and vertically.
-	 * When scaling rows horizontally, we always read forwards through
-	 * the source, and store either forwards or in reverse as required.
-	 * When scaling vertically, we always store out forwards, but may
-	 * feed source rows in in a different order.
+	/* The (x,y) position given describes where the top left corner
+	 * of the source image should be mapped to (i.e. where (0,0) in image
+	 * space ends up). Also there are differences in the way we scale
+	 * horizontally and vertically. When scaling rows horizontally, we
+	 * always read forwards through the source, and store either forwards
+	 * or in reverse as required. When scaling vertically, we always store
+	 * out forwards, but may feed source rows in in a different order.
 	 *
 	 * Consider the image rectangle 'r' to which the image is mapped,
 	 * and the (possibly) larger rectangle 'R', given by expanding 'r' to
@@ -1240,7 +1238,7 @@ fz_scale_pixmap(fz_context *ctx, fz_pixmap *src, float x, float y, float w, floa
 	{
 		float tmp;
 		w = -w;
-		dst_x_int = floor(x-w);
+		dst_x_int = floorf(x-w);
 		tmp = ceilf(x);
 		dst_w_int = (int)tmp;
 		x = tmp - x;
@@ -1248,27 +1246,29 @@ fz_scale_pixmap(fz_context *ctx, fz_pixmap *src, float x, float y, float w, floa
 	}
 	else
 	{
-		dst_x_int = floor(x);
+		dst_x_int = floorf(x);
 		x -= (float)dst_x_int;
 		dst_w_int = (int)ceilf(x + w);
 	}
 	flip_y = (h < 0);
-	/* dst_y_int is calculated to be the bottom of the scaled image, but
-	 * y (the sub pixel offset) has to end up being the value at the top.
+	/* dst_y_int is calculated to be the top of the scaled image, and
+	 * y (the sub pixel offset) is the distance in from either the top
+	 * or bottom pixel expanded edge.
 	 */
 	if (flip_y)
 	{
+		float tmp;
 		h = -h;
-		dst_y_int = floor(y-h);
-		dst_h_int = (int)ceilf(y) - dst_y_int;
+		dst_y_int = floorf(y-h);
+		tmp = ceilf(y);
+		dst_h_int = (int)tmp;
+		y = tmp - y;
+		dst_h_int -= dst_y_int;
 	} else {
-		dst_y_int = floor(y);
-		y += h;
-		dst_h_int = (int)ceilf(y) - dst_y_int;
+		dst_y_int = floorf(y);
+		y -= (float)dst_y_int;
+		dst_h_int = (int)ceilf(y + h);
 	}
-	/* y is the top edge position in floats. We want it to be the
-	 * distance down from the next pixel boundary. */
-	y = ceilf(y) - y;
 
 	DBUG(("Result image: (%d,%d) at (%d,%d) (subpix=%g,%g)\n", dst_w_int, dst_h_int, dst_x_int, dst_y_int, x, y));
 
diff --git a/draw/draw_simple_scale.c b/draw/draw_simple_scale.c
index b3a76565..1329b0e0 100644
--- a/draw/draw_simple_scale.c
+++ b/draw/draw_simple_scale.c
@@ -1192,15 +1192,13 @@ fz_scale_pixmap(fz_context *ctx, fz_pixmap *src, float x, float y, float w, floa
 
 	/* Find the destination bbox, width/height, and sub pixel offset,
 	 * allowing for whether we're flipping or not. */
-	/* Note that the x and y sub pixel offsets here are different.
-	 * The (x,y) position given describes where the bottom left corner
-	 * of the source image should be mapped to (i.e. where (0,h) in image
-	 * space ends up, not the more logical and sane (0,0)). Also there
-	 * are differences in the way we scale horizontally and vertically.
-	 * When scaling rows horizontally, we always read forwards through
-	 * the source, and store either forwards or in reverse as required.
-	 * When scaling vertically, we always store out forwards, but may
-	 * feed source rows in in a different order.
+	/* The (x,y) position given describes where the top left corner of the
+	 * source image should be mapped to (i.e. where (0,0) in image space ends
+	 * up). Also there are differences in the way we scale horizontally and
+	 * vertically. When scaling rows horizontally, we always read forwards
+	 * through the source, and store either forwards or in reverse as required.
+	 * When scaling vertically, we always store out forwards, but may feed
+	 * source rows in in a different order.
 	 *
 	 * Consider the image rectangle 'r' to which the image is mapped,
 	 * and the (possibly) larger rectangle 'R', given by expanding 'r' to
@@ -1218,7 +1216,7 @@ fz_scale_pixmap(fz_context *ctx, fz_pixmap *src, float x, float y, float w, floa
 	{
 		float tmp;
 		w = -w;
-		dst_x_int = floor(x-w);
+		dst_x_int = floorf(x-w);
 		tmp = ceilf(x);
 		dst_w_int = (int)tmp;
 		x = tmp - x;
@@ -1226,27 +1224,31 @@ fz_scale_pixmap(fz_context *ctx, fz_pixmap *src, float x, float y, float w, floa
 	}
 	else
 	{
-		dst_x_int = floor(x);
+		dst_x_int = floorf(x);
 		x -= (float)dst_x_int;
 		dst_w_int = (int)ceilf(x + w);
 	}
-	flip_y = (h < 0);
-	/* dst_y_int is calculated to be the bottom of the scaled image, but
-	 * y (the sub pixel offset) has to end up being the value at the top.
+	/* dst_y_int is calculated to be the top of the scaled image, and
+	 * y (the sub_pixel_offset) is the distance in from either the top
+	 * or bottom pixel expanded edge.
 	 */
+	flip_y = (h < 0);
 	if (flip_y)
 	{
+		float tmp;
 		h = -h;
-		dst_y_int = floor(y-h);
-		dst_h_int = (int)ceilf(y) - dst_y_int;
-	} else {
-		dst_y_int = floor(y);
-		y += h;
-		dst_h_int = (int)ceilf(y) - dst_y_int;
+		dst_y_int = floorf(y-h);
+		tmp = ceilf(y);
+		dst_h_int = (int)tmp;
+		y = tmp - y;
+		dst_h_int -= dst_y_int;
+	}
+	else
+	{
+		dst_y_int = floorf(y);
+		y -= (float)dst_y_int;
+		dst_h_int = (int)ceilf(y + h);
 	}
-	/* y is the top edge position in floats. We want it to be the
-	 * distance down from the next pixel boundary. */
-	y = ceilf(y) - y;
 
 	DBUG(("Result image: (%d,%d) at (%d,%d) (subpix=%g,%g)\n", dst_w_int, dst_h_int, dst_x_int, dst_y_int, x, y));