Introduce fz_function type.

Make pdf_functions be derived from these. This is to prepare
for transfer function support.

include/mupdf/fitz/device.h

@@ -106,6 +106,63 @@ int fz_lookup_blendmode(const char *name);
 */
 const char *fz_blendmode_name(int blendmode);
 
+/*
+	Generic function type.
+
+	Different function implementations will derive from this.
+*/
+typedef struct fz_function fz_function;
+
+typedef void (fz_function_eval_fn)(fz_context *, fz_function *, const float *, float *);
+
+enum
+{
+	FZ_FUNCTION_MAX_N = FZ_MAX_COLORS,
+	FZ_FUNCTION_MAX_M = FZ_MAX_COLORS
+};
+
+struct fz_function
+{
+	fz_storable storable;
+	size_t size;
+	int m;					/* number of input values */
+	int n;					/* number of output values */
+
+	fz_function_eval_fn *eval;
+};
+
+fz_function *fz_new_function_of_size(fz_context *ctx, int size, size_t size2, int m, int n, fz_function_eval_fn *eval, fz_store_drop_fn *drop);
+
+#define fz_new_derived_function(CTX,TYPE,SIZE,M,N,EVAL,DROP) \
+	((TYPE*)Memento_label(fz_new_function_of_size(CTX,sizeof(TYPE),SIZE,M,N,EVAL,DROP), #TYPE))
+
+/*
+	Evaluate a function.
+
+	Input vector = (in[0], ..., in[inlen-1])
+	Output vector = (out[0], ..., out[outlen-1])
+
+	If inlen or outlen do not match that expected by the function, this
+	routine will truncate or extend the input/output (with 0's) as
+	required.
+*/
+void fz_eval_function(fz_context *ctx, fz_function *func, const float *in, int inlen, float *out, int outlen);
+
+/*
+	Keep a function reference.
+*/
+fz_function *fz_keep_function(fz_context *ctx, fz_function *func);
+
+/*
+	Drop a function reference.
+*/
+void fz_drop_function(fz_context *ctx, fz_function *func);
+
+/*
+	Function size
+*/
+size_t fz_function_size(fz_context *ctx, fz_function *func);
+
 /**
 	The device structure is public to allow devices to be
 	implemented outside of fitz.

source/fitz/device.c

@@ -837,3 +837,64 @@ fz_structure_from_string(const char *str)
 	if (!strcmp(str, "Form")) return FZ_STRUCTURE_FORM;
 	return FZ_STRUCTURE_INVALID;
 }
+
+fz_function *
+fz_keep_function(fz_context *ctx, fz_function *func)
+{
+	return fz_keep_storable(ctx, &func->storable);
+}
+
+void
+fz_drop_function(fz_context *ctx, fz_function *func)
+{
+	fz_drop_storable(ctx, &func->storable);
+}
+
+size_t
+fz_function_size(fz_context *ctx, fz_function *func)
+{
+	return (func ? func->size : 0);
+}
+
+void
+fz_eval_function(fz_context *ctx, fz_function *func, const float *in, int inlen, float *out, int outlen)
+{
+	float fakein[FZ_FUNCTION_MAX_M];
+	float fakeout[FZ_FUNCTION_MAX_N];
+	int i;
+
+	if (inlen < func->m)
+	{
+		for (i = 0; i < inlen; ++i)
+			fakein[i] = in[i];
+		for (; i < func->m; ++i)
+			fakein[i] = 0;
+		in = fakein;
+	}
+
+	if (outlen < func->n)
+	{
+		func->eval(ctx, func, in, fakeout);
+		for (i = 0; i < outlen; ++i)
+			out[i] = fakeout[i];
+	}
+	else
+	{
+		func->eval(ctx, func, in, out);
+		for (i = func->n; i < outlen; ++i)
+			out[i] = 0;
+	}
+}
+
+fz_function *
+fz_new_function_of_size(fz_context *ctx, int size, size_t size2, int m, int n, fz_function_eval_fn *eval, fz_store_drop_fn *drop)
+{
+	fz_function *fn = fz_calloc(ctx, 1, size);
+
+	FZ_INIT_STORABLE(fn, 1, drop);
+	fn->eval = eval;
+	fn->m = m;
+	fn->n = n;
+
+	return fn;
+}