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diff --git a/src/display/nr-filter-utils.h b/src/display/nr-filter-utils.h
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+// SPDX-License-Identifier: GPL-2.0-or-later
+#ifndef SEEN_NR_FILTER_UTILS_H
+#define SEEN_NR_FILTER_UTILS_H
+
+/**
+ * @file
+ * Definition of functions needed by several filters.
+ */
+/*
+ * Authors:
+ *   Jean-Rene Reinhard <jr@komite.net>
+ *
+ * Copyright (C) 2007 authors
+ *
+ * Released under GNU GPL v2+, read the file 'COPYING' for more information.
+ */
+
+namespace Inkscape {
+namespace Filters {
+
+/**
+ * Clamps an integer value to a value between 0 and 255. Needed by filters where
+ * rendering computations can lead to component values out of bound.
+ *
+ * \return 0 if the value is smaller than 0, 255 if it is greater 255, else v
+ * \param v the value to clamp
+ */
+inline int clamp(int const val) {
+    if (val < 0) return 0;
+    if (val > 255) return 255;
+    return val;
+}
+
+/**
+ * Clamps an integer value to a value between 0 and 255^3.
+ *
+ * \return 0 if the value is smaller than 0, 255^3 (16581375) if it is greater than 255^3, else v
+ * \param v the value to clamp
+ */
+inline int clamp3(int const val) {
+    if (val < 0) return 0;
+    if (val > 16581375) return 16581375;
+    return val;
+}
+
+/**
+ * Macro to use the clamp function with double inputs and unsigned char output
+ */
+#define CLAMP_D_TO_U8(v) (unsigned char) clamp((int)round((v)))
+
+/**
+ * Clamps an integer to a value between 0 and alpha. Useful when handling
+ * images with premultiplied alpha, as setting some of RGB channels
+ * to a value bigger than alpha confuses the alpha blending in Inkscape
+ * \return 0 if val is negative, alpha if val is bigger than alpha, val otherwise
+ * \param val the value to clamp
+ * \param alpha the maximum value to clamp to
+ */
+inline int clamp_alpha(int const val, int const alpha) {
+    if (val < 0) return 0;
+    if (val > alpha) return alpha;
+    return val;
+}
+
+/**
+ * Macro to use the clamp function with double inputs and unsigned char output
+ */
+#define CLAMP_D_TO_U8_ALPHA(v,a) (unsigned char) clamp_alpha((int)round((v)),(a))
+
+} /* namespace Filters */
+} /* namespace Inkscape */
+
+#endif /* __NR_FILTER_UTILS_H__ */
+/*
+  Local Variables:
+  mode:c++
+  c-file-style:"stroustrup"
+  c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
+  indent-tabs-mode:nil
+  fill-column:99
+  End:
+*/
+// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :