Improve banding API.

Previously the API assumed that all bands had to be the same
height. By moving the multiplication into the caller, we can
lift that assumption.

3 files changed, 11 insertions, 15 deletions

diff --git a/source/fitz/halftone.c b/source/fitz/halftone.c
index 04c3b5f9..eb35dbdf 100644
--- a/source/fitz/halftone.c
+++ b/source/fitz/halftone.c
@@ -511,7 +511,7 @@ static int gcd(int u, int v)
 	while (1);
 }
 
-fz_bitmap *fz_new_bitmap_from_pixmap_band(fz_context *ctx, fz_pixmap *pix, fz_halftone *ht, int band, int bandheight)
+fz_bitmap *fz_new_bitmap_from_pixmap_band(fz_context *ctx, fz_pixmap *pix, fz_halftone *ht, int band_start, int bandheight)
 {
 	fz_bitmap *out = NULL;
 	unsigned char *ht_line = NULL;
@@ -528,7 +528,6 @@ fz_bitmap *fz_new_bitmap_from_pixmap_band(fz_context *ctx, fz_pixmap *pix, fz_ha
 	fz_var(ht_line);
 	fz_var(out);
 
-	band *= bandheight;
 	n = pix->n;
 
 	switch(n)
@@ -572,7 +571,7 @@ fz_bitmap *fz_new_bitmap_from_pixmap_band(fz_context *ctx, fz_pixmap *pix, fz_ha
 
 		h = pix->h;
 		x = pix->x;
-		y = pix->y + band;
+		y = pix->y + band_start;
 		w = pix->w;
 		ostride = out->stride;
 		pstride = pix->stride;
diff --git a/source/fitz/output-png.c b/source/fitz/output-png.c
index 74f2ca3f..00eaeee8 100644
--- a/source/fitz/output-png.c
+++ b/source/fitz/output-png.c
@@ -130,7 +130,7 @@ fz_write_png_header(fz_context *ctx, fz_output *out, int w, int h, int n, int al
 }
 
 void
-fz_write_png_band(fz_context *ctx, fz_output *out, fz_png_output_context *poc, int stride, int band, int bandheight, unsigned char *sp)
+fz_write_png_band(fz_context *ctx, fz_output *out, fz_png_output_context *poc, int stride, int band_start, int bandheight, unsigned char *sp)
 {
 	unsigned char *dp;
 	int y, x, k, err, finalband;
@@ -144,10 +144,9 @@ fz_write_png_band(fz_context *ctx, fz_output *out, fz_png_output_context *poc, i
 	n = poc->n;
 	alpha = poc->alpha;
 
-	band *= bandheight;
-	finalband = (band+bandheight >= h);
+	finalband = (band_start+bandheight >= h);
 	if (finalband)
-		bandheight = h - band;
+		bandheight = h - band_start;
 
 	if (poc->udata == NULL)
 	{
diff --git a/source/fitz/output-pnm.c b/source/fitz/output-pnm.c
index e253d96a..99edc24d 100644
--- a/source/fitz/output-pnm.c
+++ b/source/fitz/output-pnm.c
@@ -20,12 +20,11 @@ fz_write_pnm_header(fz_context *ctx, fz_output *out, int w, int h, int n, int al
 }
 
 void
-fz_write_pnm_band(fz_context *ctx, fz_output *out, int w, int h, int n, int alpha, int stride, int band, int bandheight, unsigned char *p)
+fz_write_pnm_band(fz_context *ctx, fz_output *out, int w, int h, int n, int alpha, int stride, int band_start, int bandheight, unsigned char *p)
 {
 	char buffer[2*3*4*5*6]; /* Buffer must be a multiple of 2 and 3 at least. */
 	int len;
-	int start = band * bandheight;
-	int end = start + bandheight;
+	int end = band_start + bandheight;
 
 	if (n-alpha != 1 && n-alpha != 3)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "pixmap must be grayscale or rgb to write as pnm");
@@ -35,7 +34,7 @@ fz_write_pnm_band(fz_context *ctx, fz_output *out, int w, int h, int n, int alph
 
 	if (end > h)
 		end = h;
-	end -= start;
+	end -= band_start;
 
 	/* Tests show that writing single bytes out at a time
 	 * is appallingly slow. We get a huge improvement
@@ -135,18 +134,17 @@ fz_write_pam_header(fz_context *ctx, fz_output *out, int w, int h, int n, int al
 }
 
 void
-fz_write_pam_band(fz_context *ctx, fz_output *out, int w, int h, int n, int stride, int band, int bandheight, unsigned char *sp)
+fz_write_pam_band(fz_context *ctx, fz_output *out, int w, int h, int n, int stride, int band_start, int bandheight, unsigned char *sp)
 {
 	int y;
-	int start = band * bandheight;
-	int end = start + bandheight;
+	int end = band_start + bandheight;
 
 	if (!out)
 		return;
 
 	if (end > h)
 		end = h;
-	end -= start;
+	end -= band_start;
 
 	for (y = 0; y < end; y++)
 	{