Warn about out of range values for exponential pdf functions

Exponential pdf functions have constraints on their input values so
warn about out of range values when loading those functions. When
evaluation the functions, assume zero without warning.

1 files changed, 18 insertions, 6 deletions

diff --git a/pdf/pdf_function.c b/pdf/pdf_function.c
index 5eea4125..005572df 100644
--- a/pdf/pdf_function.c
+++ b/pdf/pdf_function.c
@@ -1137,10 +1137,25 @@ load_exponential_func(fz_context *ctx, pdf_function *func, pdf_obj *dict)
 	func->m = 1;
 
 	obj = pdf_dict_gets(dict, "N");
-	if (!pdf_is_int(obj) && !pdf_is_real(obj))
-		fz_throw(ctx, "malformed /N");
 	func->u.e.n = pdf_to_real(obj);
 
+	/* See exponential functions (PDF 1.7 section 3.9.2) */
+	if (func->u.e.n != (int) func->u.e.n)
+	{
+		/* If N is non-integer, input values may never be negative */
+		for (i = 0; i < func->m; i++)
+			if (func->domain[i][0] < 0 || func->domain[i][1] < 0)
+				fz_warn(ctx, "exponential function input domain includes illegal negative input values");
+	}
+	else if (func->u.e.n < 0)
+	{
+		/* if N is negative, input values may never be zero */
+		for (i = 0; i < func->m; i++)
+			if (func->domain[i][0] == 0 || func->domain[i][1] == 0 ||
+				(func->domain[i][0] < 0 && func->domain[i][1] > 0))
+				fz_warn(ctx, "exponential function input domain includes illegal input value zero");
+	}
+
 	obj = pdf_dict_gets(dict, "C0");
 	if (pdf_is_array(obj))
 	{
@@ -1181,12 +1196,9 @@ eval_exponential_func(fz_context *ctx, pdf_function *func, float in, float *out)
 
 	x = fz_clamp(x, func->domain[0][0], func->domain[0][1]);
 
-	/* constraint */
+	/* Default output is zero, which is suitable for violated constraints */
 	if ((func->u.e.n != (int)func->u.e.n && x < 0) || (func->u.e.n < 0 && x == 0))
-	{
-		fz_warn(ctx, "constraint error");
 		return;
-	}
 
 	tmp = powf(x, func->u.e.n);
 	for (i = 0; i < func->n; i++)