Pixmap writers for formats with alpha should handle premultiplied data.

Any pixmap writers that can handle data with an alpha plane
should accept that data in premultiplied form, and write it out
appropriately for the file format.

This avoids the need to unpremultiply data in mudraw, and solves
the issue we were seeing where we want the png writer to be able
to cope with premultiplied data (such as for the debug blending
routines) and unpremultiplied data (such as that given after
mudraw has unpremultiplied the data).

1 files changed, 66 insertions, 7 deletions

diff --git a/source/fitz/output-psd.c b/source/fitz/output-psd.c
index 223a591e..e097e9a6 100644
--- a/source/fitz/output-psd.c
+++ b/source/fitz/output-psd.c
@@ -254,8 +254,41 @@ psd_write_band(fz_context *ctx, fz_band_writer *writer_, int stride, int band_st
 	plane_inc = w * (h - band_height);
 	line_skip = stride - w*n;
 	b = buffer;
-	for (k = 0; k < n; k++)
+	if (writer->super.alpha)
 	{
+		const unsigned char *ap = &sp[n-1];
+		for (k = 0; k < n-1; k++)
+		{
+			for (y = 0; y < band_height; y++)
+			{
+				for (x = 0; x < w; x++)
+				{
+					int a = *ap;
+					ap += n;
+					*b++ = a != 0 ? (*sp * 255 + 128)/a : 0;
+					sp += n;
+					if (b == buffer_end)
+					{
+						if (k >= num_additive)
+							psd_invert_buffer(buffer, sizeof(buffer));
+						fz_write_data(ctx, out, buffer, sizeof(buffer));
+						b = buffer;
+					}
+				}
+				sp += line_skip;
+				ap += line_skip;
+			}
+			sp -= stride * band_height - 1;
+			ap -= stride * band_height;
+			if (b != buffer)
+			{
+				if (k >= num_additive)
+					psd_invert_buffer(buffer, sizeof(buffer));
+				fz_write_data(ctx, out, buffer, b - buffer);
+				b = buffer;
+			}
+			fz_seek_output(ctx, out, plane_inc, SEEK_CUR);
+		}
 		for (y = 0; y < band_height; y++)
 		{
 			for (x = 0; x < w; x++)
@@ -264,25 +297,51 @@ psd_write_band(fz_context *ctx, fz_band_writer *writer_, int stride, int band_st
 				sp += n;
 				if (b == buffer_end)
 				{
-					if (k >= num_additive)
-						psd_invert_buffer(buffer, sizeof(buffer));
 					fz_write_data(ctx, out, buffer, sizeof(buffer));
 					b = buffer;
 				}
 			}
 			sp += line_skip;
 		}
-		sp -= stride * band_height - 1;
 		if (b != buffer)
 		{
-			if (k >= num_additive)
-				psd_invert_buffer(buffer, sizeof(buffer));
 			fz_write_data(ctx, out, buffer, b - buffer);
 			b = buffer;
 		}
 		fz_seek_output(ctx, out, plane_inc, SEEK_CUR);
 	}
-	fz_seek_output(ctx, out, w * h * (1-n), SEEK_CUR);
+	else
+	{
+		for (k = 0; k < n; k++)
+		{
+			for (y = 0; y < band_height; y++)
+			{
+				for (x = 0; x < w; x++)
+				{
+					*b++ = *sp;
+					sp += n;
+					if (b == buffer_end)
+					{
+						if (k >= num_additive)
+							psd_invert_buffer(buffer, sizeof(buffer));
+						fz_write_data(ctx, out, buffer, sizeof(buffer));
+						b = buffer;
+					}
+				}
+				sp += line_skip;
+			}
+			sp -= stride * band_height - 1;
+			if (b != buffer)
+			{
+				if (k >= num_additive)
+					psd_invert_buffer(buffer, sizeof(buffer));
+				fz_write_data(ctx, out, buffer, b - buffer);
+				b = buffer;
+			}
+			fz_seek_output(ctx, out, plane_inc, SEEK_CUR);
+		}
+	}
+	fz_seek_output(ctx, out, w * (band_height - h * n), SEEK_CUR);
 }
 
 static void