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, 112 insertions, 42 deletions

diff --git a/source/fitz/output-pnm.c b/source/fitz/output-pnm.c
index 9bc5e6aa..598d66f6 100644
--- a/source/fitz/output-pnm.c
+++ b/source/fitz/output-pnm.c
@@ -15,6 +15,9 @@ pnm_write_header(fz_context *ctx, fz_band_writer *writer, const fz_colorspace *c
 	if (writer->s != 0)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "PNM writer cannot cope with spot colors");
 
+	if (alpha)
+		fz_throw(ctx, FZ_ERROR_GENERIC, "PNM writer cannot cope with alpha");
+
 	n -= alpha;
 	if (n != 1 && n != 3)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "pixmap must be grayscale or rgb to write as pnm");
@@ -34,12 +37,10 @@ pnm_write_band(fz_context *ctx, fz_band_writer *writer, int stride, int band_sta
 	int w = writer->w;
 	int h = writer->h;
 	int n = writer->n;
-	int alpha = writer->alpha;
-	char buffer[2*3*4*5*6]; /* Buffer must be a multiple of 2 and 3 at least. */
 	int len;
 	int end = band_start + band_height;
 
-	if (n-alpha != 1 && n-alpha != 3)
+	if (n != 1 && n != 3)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "pixmap must be grayscale or rgb to write as pnm");
 
 	if (!out)
@@ -67,44 +68,10 @@ pnm_write_band(fz_context *ctx, fz_band_writer *writer, int stride, int band_sta
 				fz_write_data(ctx, out, p, num_written);
 				p += num_written;
 				break;
-			case 2:
-			{
-				char *o = buffer;
-				int count;
-
-				if (num_written > sizeof(buffer))
-					num_written = sizeof(buffer);
-
-				for (count = num_written; count; count--)
-				{
-					*o++ = *p;
-					p += 2;
-				}
-				fz_write_data(ctx, out, buffer, num_written);
-				break;
-			}
 			case 3:
 				fz_write_data(ctx, out, p, num_written*3);
 				p += num_written*3;
 				break;
-			case 4:
-			{
-				char *o = buffer;
-				int count;
-
-				if (num_written > sizeof(buffer)/3)
-					num_written = sizeof(buffer)/3;
-
-				for (count = num_written; count; count--)
-				{
-					*o++ = p[0];
-					*o++ = p[1];
-					*o++ = p[2];
-					p += n;
-				}
-				fz_write_data(ctx, out, buffer, num_written * 3);
-				break;
-			}
 			}
 			len -= num_written;
 		}
@@ -191,7 +158,7 @@ pam_write_header(fz_context *ctx, fz_band_writer *writer, const fz_colorspace *c
 	else if (n == 3 && !alpha) fz_write_printf(ctx, out, "TUPLTYPE RGB\n");
 	else if (n == 3 && alpha) fz_write_printf(ctx, out, "TUPLTYPE RGB_ALPHA\n");
 	else if (n == 4 && !alpha) fz_write_printf(ctx, out, "TUPLTYPE CMYK\n");
-	else if (n == 5) fz_write_printf(ctx, out, "TUPLTYPE CMYK_ALPHA\n");
+	else if (n == 4 && alpha) fz_write_printf(ctx, out, "TUPLTYPE CMYK_ALPHA\n");
 	fz_write_printf(ctx, out, "ENDHDR\n");
 }
 
@@ -202,7 +169,8 @@ pam_write_band(fz_context *ctx, fz_band_writer *writer, int stride, int band_sta
 	int w = writer->w;
 	int h = writer->h;
 	int n = writer->n;
-	int y;
+	int alpha = writer->alpha;
+	int x, y;
 	int end = band_start + band_height;
 
 	if (!out)
@@ -212,11 +180,113 @@ pam_write_band(fz_context *ctx, fz_band_writer *writer, int stride, int band_sta
 		end = h;
 	end -= band_start;
 
-	for (y = 0; y < end; y++)
+	if (alpha)
 	{
-		fz_write_data(ctx, out, sp, w * n);
-		sp += stride;
+		/* Buffer must be a multiple of 2, 3 and 5 at least. */
+		/* Also, for the generic case, it must be bigger than FZ_MAX_COLORS */
+		char buffer[2*3*4*5*6];
+		char *b = buffer;
+		stride -= n * w;
+		switch (n)
+		{
+		case 2:
+			for (y = 0; y < end; y++)
+			{
+				for (x = 0; x < w; x++)
+				{
+					int a = sp[1];
+					*b++ = a ? (sp[0] * 255 + (a>>1))/a : 0;
+					*b++ = a;
+					sp += 2;
+					if (b == &buffer[sizeof(buffer)])
+					{
+						fz_write_data(ctx, out, buffer, sizeof(buffer));
+						b = buffer;
+					}
+				}
+				sp += stride;
+			}
+			if (b != buffer)
+				fz_write_data(ctx, out, buffer, b - buffer);
+			break;
+		case 4:
+			for (y = 0; y < end; y++)
+			{
+				for (x = 0; x < w; x++)
+				{
+					int a = sp[3];
+					int inva = a ? 256 * 255 / a : 0;
+					*b++ = (sp[0] * inva + 128)>>8;
+					*b++ = (sp[1] * inva + 128)>>8;
+					*b++ = (sp[2] * inva + 128)>>8;
+					*b++ = a;
+					sp += 4;
+					if (b == &buffer[sizeof(buffer)])
+					{
+						fz_write_data(ctx, out, buffer, sizeof(buffer));
+						b = buffer;
+					}
+				}
+				sp += stride;
+			}
+			if (b != buffer)
+				fz_write_data(ctx, out, buffer, b - buffer);
+			break;
+		case 5:
+			for (y = 0; y < end; y++)
+			{
+				for (x = 0; x < w; x++)
+				{
+					int a = sp[4];
+					int inva = a ? 256 * 255 / a : 0;
+					*b++ = (sp[0] * inva + 128)>>8;
+					*b++ = (sp[1] * inva + 128)>>8;
+					*b++ = (sp[2] * inva + 128)>>8;
+					*b++ = (sp[3] * inva + 128)>>8;
+					*b++ = a;
+					sp += 5;
+					if (b == &buffer[sizeof(buffer)])
+					{
+						fz_write_data(ctx, out, buffer, sizeof(buffer));
+						b = buffer;
+					}
+				}
+				sp += stride;
+			}
+			if (b != buffer)
+				fz_write_data(ctx, out, buffer, b - buffer);
+			break;
+		default:
+			for (y = 0; y < end; y++)
+			{
+				for (x = 0; x < w; x++)
+				{
+					int a = sp[n-1];
+					int inva = a ? 256 * 255 / a : 0;
+					int k;
+					for (k = 0; k < n-1; k++)
+						*b++ = (*sp++ * inva + 128)>>8;
+					*b++ = a;
+					sp++;
+					if (b >= &buffer[sizeof(buffer)] - n)
+					{
+						fz_write_data(ctx, out, buffer, b - buffer);
+						b = buffer;
+					}
+				}
+				sp += stride;
+			}
+			if (b != buffer)
+				fz_write_data(ctx, out, buffer, b - buffer);
+			break;
+		}
 	}
+	else
+		for (y = 0; y < end; y++)
+		{
+			fz_write_data(ctx, out, sp, w * n);
+			sp += stride;
+		}
 }
 
 fz_band_writer *fz_new_pam_band_writer(fz_context *ctx, fz_output *out)