From 95dcd22b461d0f15b99bfb5290ff0141ae2fe687 Mon Sep 17 00:00:00 2001
From: "dumitru.stama" <dumitru.stama@gmail.com>
Date: Wed, 14 Jun 2017 00:55:52 -0700
Subject: [PATCH] Added a new 'blend_rect' method acting as 'blit_rect' with
 alpha-blending

---
 core/image.cpp        | 46 +++++++++++++++++++++++++++++++++++++++++++
 core/image.h          |  1 +
 core/variant_call.cpp |  2 ++
 doc/base/classes.xml  | 11 +++++++++++
 4 files changed, 60 insertions(+)

diff --git a/core/image.cpp b/core/image.cpp
index df29879f163..56f09d8f8c1 100644
--- a/core/image.cpp
+++ b/core/image.cpp
@@ -2217,6 +2217,52 @@ void Image::blit_rect(const Image &p_src, const Rect2 &p_src_rect, const Point2
 	}
 }
 
+void Image::blend_rect(const Image &p_src, const Rect2 &p_src_rect, const Point2 &p_dest) {
+
+	int dsize = data.size();
+	int srcdsize = p_src.data.size();
+	int dst_data_size = data.size();
+	ERR_FAIL_COND(dsize == 0);
+	ERR_FAIL_COND(srcdsize == 0);
+	ERR_FAIL_COND(dst_data_size == 0);
+
+	Rect2 rrect = Rect2(0, 0, p_src.width, p_src.height).clip(p_src_rect);
+
+	DVector<uint8_t>::Write wp = data.write();
+	unsigned char *dst_data_ptr = wp.ptr();
+
+	DVector<uint8_t>::Read rp = p_src.data.read();
+	const unsigned char *src_data_ptr = rp.ptr();
+
+	if (format == FORMAT_INDEXED || format == FORMAT_INDEXED || p_src.format == FORMAT_INDEXED || p_src.format == FORMAT_INDEXED_ALPHA) {
+
+		return;
+
+	} else {
+
+		for (int i = 0; i < rrect.size.y; i++) {
+
+			if (i + p_dest.y < 0 || i + p_dest.y >= height)
+				continue;
+			for (int j = 0; j < rrect.size.x; j++) {
+
+				if (j + p_dest.x < 0 || j + p_dest.x >= width)
+					continue;
+
+				BColor src = p_src._get_pixel(rrect.pos.x + j, rrect.pos.y + i, src_data_ptr, srcdsize);
+				BColor dst = _get_pixel(p_dest.x + j, p_dest.y + i, dst_data_ptr, dst_data_size);
+				float ba = (float) dst.a / 255.0;
+				float fa = (float) src.a / 255.0;
+				dst.r = (uint8_t) (fa*src.r + ba*(1.0 - fa) * dst.r);
+				dst.g = (uint8_t) (fa*src.g + ba*(1.0 - fa) * dst.g);
+				dst.b = (uint8_t) (fa*src.b + ba*(1.0 - fa) * dst.b);
+				dst.a = (uint8_t) (255.0 * (fa + ba * (1.0 - fa)));
+				_put_pixel(p_dest.x + j, p_dest.y + i, dst, dst_data_ptr);
+			}
+		}
+	}
+}
+
 Image (*Image::_png_mem_loader_func)(const uint8_t *, int) = NULL;
 Image (*Image::_jpg_mem_loader_func)(const uint8_t *, int) = NULL;
 
diff --git a/core/image.h b/core/image.h
index e727b004eb1..4156d6a6ac5 100644
--- a/core/image.h
+++ b/core/image.h
@@ -351,6 +351,7 @@ public:
 	void normalmap_to_xy();
 
 	void blit_rect(const Image &p_src, const Rect2 &p_src_rect, const Point2 &p_dest);
+	void blend_rect(const Image &p_src, const Rect2 &p_src_rect, const Point2 &p_dest);
 	void brush_transfer(const Image &p_src, const Image &p_brush, const Point2 &p_dest);
 	Image brushed(const Image &p_src, const Image &p_brush, const Point2 &p_dest) const;
 
diff --git a/core/variant_call.cpp b/core/variant_call.cpp
index 01a3b4a1b03..878bd55dcac 100644
--- a/core/variant_call.cpp
+++ b/core/variant_call.cpp
@@ -619,6 +619,7 @@ struct _VariantCall {
 	VCALL_PTR3R(Image, resized);
 	VCALL_PTR0R(Image, get_data);
 	VCALL_PTR3(Image, blit_rect);
+	VCALL_PTR3(Image, blend_rect);
 	VCALL_PTR1R(Image, converted);
 	VCALL_PTR0(Image, fix_alpha_edges);
 
@@ -1467,6 +1468,7 @@ void register_variant_methods() {
 	ADDFUNC3(IMAGE, IMAGE, Image, resized, INT, "x", INT, "y", INT, "interpolation", varray(((int)Image::INTERPOLATE_BILINEAR)));
 	ADDFUNC0(IMAGE, RAW_ARRAY, Image, get_data, varray());
 	ADDFUNC3(IMAGE, NIL, Image, blit_rect, IMAGE, "src", RECT2, "src_rect", VECTOR2, "dest", varray(0));
+	ADDFUNC3(IMAGE, NIL, Image, blend_rect, IMAGE, "src", RECT2, "src_rect", VECTOR2, "dest", varray(0));
 	ADDFUNC1(IMAGE, IMAGE, Image, converted, INT, "format", varray(0));
 	ADDFUNC0(IMAGE, NIL, Image, fix_alpha_edges, varray());
 
diff --git a/doc/base/classes.xml b/doc/base/classes.xml
index c8c09e82a9e..33d476b64f0 100644
--- a/doc/base/classes.xml
+++ b/doc/base/classes.xml
@@ -15855,6 +15855,17 @@
 				Create an empty image of a specific size and format.
 			</description>
 		</method>
+		<method name="blend_rect">
+			<argument index="0" name="src" type="Image">
+			</argument>
+			<argument index="1" name="src_rect" type="Rect2">
+			</argument>
+			<argument index="2" name="dest" type="Vector2" default="0">
+			</argument>
+			<description>
+				Alpha-blends a "src_rect" [Rect2] from "src" [Image] to this [Image] on coordinates "dest".
+			</description>
+		</method>
 		<method name="blit_rect">
 			<argument index="0" name="src" type="Image">
 			</argument>