pdf_function.c

SumatraPDF是一款小型开源的pdf阅读工具。虽然玲珑小巧（只有800多KB）

	/* encode input coordinates */
	for (i = 0; i < func->m; i++)
	{
		x = CLAMP(in[i], func->domain[i][0], func->domain[i][1]);
		x = LERP(x, func->domain[i][0], func->domain[i][1],
				func->u.sa.encode[i][0], func->u.sa.encode[i][1]);
		x = CLAMP(x, 0, func->u.sa.size[i] - 1);
		e[0][i] = floor(x);
		e[1][i] = ceil(x);
		efrac[i] = x - floor(x);
	}

	if (func->m > 4)
	{
		s0 = fz_malloc((1 << func->m) * 2 * sizeof(float));
		s1 = s0 + (1 << func->m);
		if (!s0)
			return fz_throw("outofmem: scratch buffer");
	}

	/* FIXME i think this is wrong... test with 2 samples it gets wrong idxs */
	for (i = 0; i < func->n; i++)
	{
		/* pull 2^m values out of the sample array */
		for (j = 0; j < (1 << func->m); ++j)
		{
			idx = 0;
			for (k = func->m - 1; k >= 0; --k)
				idx = idx * func->u.sa.size[k] + e[(j >> k) & 1][k];
			idx = idx * func->n + i;
			s0[j] = func->u.sa.samples[idx];
		}

		/* do m sets of interpolations */
		for (j = 0; j < func->m; ++j)
		{
			for (k = 0; k < (1 << (func->m - j)); k += 2)
				s1[k >> 1] = (1 - efrac[j]) * s0[k] + efrac[j] * s0[k+1];
			memcpy(s0, s1, (1 << (func->m - j - 1)) * sizeof(float));
		}

		/* decode output values */
		out[i] = LERP(s0[0], 0, (1 << func->u.sa.bps) - 1,
				func->u.sa.decode[i][0], func->u.sa.decode[i][1]);
		out[i] = CLAMP(out[i], func->range[i][0], func->range[i][1]);
	}

	if (func->m > 4)
		fz_free(s0);

	return fz_okay;
}

/*
 * Exponential function
 */

static fz_error *
loadexponentialfunc(pdf_function *func, fz_obj *dict)
{
	fz_obj *obj;
	int i;

	pdf_logrsrc("exponential function {\n");

	if (func->m != 1)
		return fz_throw("/Domain must be one dimension (%d)", func->m);

	obj = fz_dictgets(dict, "N");
	if (!fz_isint(obj) && !fz_isreal(obj))
		return fz_throw("malformed /N");
	func->u.e.n = fz_toreal(obj);
	pdf_logrsrc("n %g\n", func->u.e.n);

	obj = fz_dictgets(dict, "C0");
	if (fz_isarray(obj))
	{
		func->n = fz_arraylen(obj);
		for (i = 0; i < func->n; ++i)
			func->u.e.c0[i] = fz_toreal(fz_arrayget(obj, i));
		pdf_logrsrc("c0 %d\n", func->n);
	}
	else
	{
		func->n = 1;
		func->u.e.c0[0] = 0;
	}

	obj = fz_dictgets(dict, "C1");
	if (fz_isarray(obj))
	{
		if (fz_arraylen(obj) != func->n)
			return fz_throw("/C1 must match /C0 length");
		for (i = 0; i < func->n; ++i)
			func->u.e.c1[i] = fz_toreal(fz_arrayget(obj, i));
		pdf_logrsrc("c1 %d\n", func->n);
	}
	else
	{
		if (func->n != 1)
			return fz_throw("/C1 must match /C0 length");
		func->u.e.c1[0] = 1;
	}

	pdf_logrsrc("}\n");

	return fz_okay;
}

static fz_error *
evalexponentialfunc(pdf_function *func, float in, float *out)
{
	float x = in;
	float tmp;
	int i;

	x = CLAMP(x, func->domain[0][0], func->domain[0][1]);

	/* constraint */
	if (func->u.e.n != (int)func->u.e.n && x < 0)
		return fz_throw("constraint error");
	if (func->u.e.n < 0 && x == 0)
		return fz_throw("constraint error");

	tmp = pow(x, func->u.e.n);
	for (i = 0; i < func->n; ++i)
	{
		out[i] = func->u.e.c0[i] + tmp * (func->u.e.c1[i] - func->u.e.c0[i]);
		if (func->hasrange)
			out[i] = CLAMP(out[i], func->range[i][0], func->range[i][1]);
	}

	return fz_okay;
}

/*
 * Stitching function
 */

static fz_error *
loadstitchingfunc(pdf_function *func, pdf_xref *xref, fz_obj *dict)
{
	pdf_function **funcs = func->u.st.funcs;
	fz_error *error;
	fz_obj *obj;
	fz_obj *sub;
	fz_obj *num;
	int k;
	int i;

	pdf_logrsrc("stitching {\n");

	func->u.st.k = 0;

	if (func->m != 1)
		return fz_throw("/Domain must be one dimension (%d)", func->m);

	obj = fz_dictgets(dict, "Functions");
	{
		error = pdf_resolve(&obj, xref);
		if (error)
			return fz_rethrow(error, "cannot resolve /Functions");

		k = fz_arraylen(obj);
		func->u.st.k = k;

		pdf_logrsrc("k %d\n", func->u.st.k);

		if (k >= MAXK)
		{
			fz_dropobj(obj);
			return fz_throw("assert: /K too big (%d)", k);
		}

		for (i = 0; i < k; ++i)
		{
			sub = fz_arrayget(obj, i);
			error = pdf_loadfunction(funcs + i, xref, sub);
			if (error)
			{
				fz_dropobj(obj);
				return fz_rethrow(error, "cannot load sub function %d", i);
			}
			if (funcs[i]->m != 1 || funcs[i]->n != funcs[0]->n)
			{
				fz_dropobj(obj);
				return fz_rethrow(error, "sub function %d /Domain or /Range mismatch", i);
			}
		}

		if (!func->n)
		{
			func->n = funcs[0]->n;
		}
		else if (func->n != funcs[0]->n)
		{
			fz_dropobj(obj);
			return fz_rethrow(error, "sub function /Domain or /Range mismatch");
		}

		fz_dropobj(obj);
	}

	obj = fz_dictgets(dict, "Bounds");
	{
		error = pdf_resolve(&obj, xref);
		if (error)
			return fz_rethrow(error, "cannot resolve /Bounds");

		if (!fz_isarray(obj) || fz_arraylen(obj) != k - 1)
		{
			fz_dropobj(obj);
			return fz_throw("malformed /Bounds (not array or wrong length)");
		}

		for (i = 0; i < k-1; ++i)
		{
			num = fz_arrayget(obj, i);
			if (!fz_isint(num) && !fz_isreal(num))
			{
				fz_dropobj(obj);
				return fz_throw("malformed /Bounds (item not number)");
			}
			func->u.st.bounds[i] = fz_toreal(num);
			if (i && func->u.st.bounds[i-1] > func->u.st.bounds[i])
			{
				fz_dropobj(obj);
				return fz_throw("malformed /Bounds (item not monotonic)");
			}
		}

		if (k != 1 &&
				(func->domain[0][0] > func->u.st.bounds[0] ||
				 func->domain[0][1] < func->u.st.bounds[k-2]))
			fz_warn("malformed shading function bounds (domain mismatch), proceeding anyway.");

		fz_dropobj(obj);
	}

	obj = fz_dictgets(dict, "Encode");
	{
		error = pdf_resolve(&obj, xref);
		if (error)
			return fz_rethrow(error, "cannot resolve /Encode");

		if (!fz_isarray(obj) || fz_arraylen(obj) != k * 2)
		{
			fz_dropobj(obj);
			return fz_throw("malformed /Encode");
		}

		for (i = 0; i < k; ++i)
		{
			func->u.st.encode[i][0] = fz_toreal(fz_arrayget(obj, i*2+0));
			func->u.st.encode[i][1] = fz_toreal(fz_arrayget(obj, i*2+1));
		}

		fz_dropobj(obj);
	}

	pdf_logrsrc("}\n");

	return fz_okay;
}

static fz_error*
evalstitchingfunc(pdf_function *func, float in, float *out)
{
	fz_error *error;
	float low, high;
	int k = func->u.st.k;
	float *bounds = func->u.st.bounds;
	int i;

	in = CLAMP(in, func->domain[0][0], func->domain[0][1]);

	for (i = 0; i < k - 1; ++i)
	{
		if (in < bounds[i])
			break;
	}

	if (i == 0 && k == 1)
	{
		low = func->domain[0][0];
		high = func->domain[0][1];
	}
	else if (i == 0)
	{
		low = func->domain[0][0];
		high = bounds[0];
	}
	else if (i == k - 1)
	{
		low = bounds[k-2];
		high = func->domain[0][1];
	}
	else
	{
		low = bounds[i-1];
		high = bounds[i];
	}

	in = LERP(in, low, high, func->u.st.encode[i][0], func->u.st.encode[i][1]);

	error = pdf_evalfunction(func->u.st.funcs[i], &in, 1, out, func->n);
	if (error)
		return fz_rethrow(error, "cannot evaluate sub function %d", i);

	return fz_okay;
}

/*
 * Common
 */

pdf_function *
pdf_keepfunction(pdf_function *func)
{
	func->refs ++;
	return func;
}

void
pdf_dropfunction(pdf_function *func)
{
	int i;
	if (--func->refs == 0)
	{
		switch(func->type)
		{
		case SAMPLE:
			fz_free(func->u.sa.samples);
			break;
		case EXPONENTIAL:
			break;
		case STITCHING:
			for (i = 0; i < func->u.st.k; ++i)
				pdf_dropfunction(func->u.st.funcs[i]);
			break;
		case POSTSCRIPT:
			fz_free(func->u.p.code);
			break;
		}
		fz_free(func);
	}
}

fz_error *
pdf_loadfunction(pdf_function **funcp, pdf_xref *xref, fz_obj *ref)
{
	fz_error *error;
	pdf_function *func;
	fz_obj *dict;
	fz_obj *obj;
	int i;

	if ((*funcp = pdf_finditem(xref->store, PDF_KFUNCTION, ref)))
	{
		pdf_keepfunction(*funcp);
		return fz_okay;
	}

	pdf_logrsrc("load function (%d %d R) {\n", fz_tonum(ref), fz_togen(ref));

	func = fz_malloc(sizeof(pdf_function));
	if (!func)
		return fz_throw("outofmem: function struct");

	memset(func, 0, sizeof(pdf_function));
	func->refs = 1;

	dict = ref;
	error = pdf_resolve(&dict, xref);
	if (error)
	{
		fz_free(func);
		return fz_rethrow(error, "cannot resolve function object");
	}

	obj = fz_dictgets(dict, "FunctionType");
	func->type = fz_toint(obj);

	pdf_logrsrc("type %d\n", func->type);

	/* required for all */
	obj = fz_dictgets(dict, "Domain");
	func->m = fz_arraylen(obj) / 2;
	for (i = 0; i < func->m; i++)
	{
		func->domain[i][0] = fz_toreal(fz_arrayget(obj, i * 2 + 0));
		func->domain[i][1] = fz_toreal(fz_arrayget(obj, i * 2 + 1));
	}
	pdf_logrsrc("domain %d\n", func->m);

	/* required for type0 and type4, optional otherwise */
	obj = fz_dictgets(dict, "Range");
	if (fz_isarray(obj))
	{
		func->hasrange = 1;
		func->n = fz_arraylen(obj) / 2;
		for (i = 0; i < func->n; i++)
		{
			func->range[i][0] = fz_toreal(fz_arrayget(obj, i * 2 + 0));
			func->range[i][1] = fz_toreal(fz_arrayget(obj, i * 2 + 1));
		}
		pdf_logrsrc("range %d\n", func->n);
	}
	else
	{
		func->hasrange = 0;
		func->n = 0;
	}

	if (func->m >= MAXM || func->n >= MAXN)
	{
		fz_free(func);
		fz_dropobj(dict);
		return fz_throw("assert: /Domain or /Range too big");
	}

	switch(func->type)
	{
	case SAMPLE:
		error = loadsamplefunc(func, xref, dict, fz_tonum(ref), fz_togen(ref));
		if (error)
		{
			pdf_dropfunction(func);
			fz_dropobj(dict);
			return fz_rethrow(error, "cannot load sampled function (%d %d R)", fz_tonum(ref), fz_togen(ref));
		}
		break;

	case EXPONENTIAL:
		error = loadexponentialfunc(func, dict);
		if (error)
		{
			pdf_dropfunction(func);
			fz_dropobj(dict);
			return fz_rethrow(error, "cannot load exponential function (%d %d R)", fz_tonum(ref), fz_togen(ref));
		}
		break;

	case STITCHING:
		error = loadstitchingfunc(func, xref, dict);
		if (error)
		{
			pdf_dropfunction(func);
			fz_dropobj(dict);
			return fz_rethrow(error, "cannot load stitching function (%d %d R)", fz_tonum(ref), fz_togen(ref));
		}
		break;

	case POSTSCRIPT:
		error = loadpostscriptfunc(func, xref, dict, fz_tonum(ref), fz_togen(ref));
		if (error)
		{
			pdf_dropfunction(func);
			fz_dropobj(dict);
			return fz_rethrow(error, "cannot load calculator function (%d %d R)", fz_tonum(ref), fz_togen(ref));
		}
		break;

	default:
		fz_free(func);
		fz_dropobj(dict);
		return fz_throw("unknown function type %d (%d %d R)", func->type, fz_tonum(ref), fz_togen(ref));
	}

	fz_dropobj(dict);

	pdf_logrsrc("}\n");

	error = pdf_storeitem(xref->store, PDF_KFUNCTION, ref, func);
	if (error)
	{
		pdf_dropfunction(func);
		fz_dropobj(dict);
		return fz_rethrow(error, "cannot store function resource");
	}

	*funcp = func;
	return fz_okay;
}

fz_error *
pdf_evalfunction(pdf_function *func, float *in, int inlen, float *out, int outlen)
{
	fz_error *error;
	float r;
	int i;

	if (func->m != inlen || func->n != outlen)
		return fz_throw("function argument count mismatch");

	switch(func->type)
	{
	case SAMPLE:
		error = evalsamplefunc(func, in, out);
		if (error)
			return fz_rethrow(error, "cannot evaluate sampled function");
		break;

	case EXPONENTIAL:
		error = evalexponentialfunc(func, *in, out);
		if (error)
			return fz_rethrow(error, "cannot evaluate exponential function");
		break;

	case STITCHING:
		error = evalstitchingfunc(func, *in, out);
		if (error)
			return fz_rethrow(error, "cannot evaluate stitching function");
		break;

	case POSTSCRIPT:
		{
			psstack st;
			psinitstack(&st);

			for (i = 0; i < func->m; ++i)
				SAFE_PUSHREAL(&st, in[i]);

			error = evalpostscriptfunc(func, &st, 0);
			if (error)
				return fz_rethrow(error, "cannot evaluate calculator function");

			for (i = func->n - 1; i >= 0; --i)
			{
				SAFE_POPNUM(&st, &r);
				out[i] = CLAMP(r, func->range[i][0], func->range[i][1]);
			}
		}
		break;

	default:
		return fz_throw("assert: unknown function type");
	}

	return fz_okay;
}