libgraphics: Fix blur algorithm

The blur algorithm had an error in the indexing for the vertical component of the blur and an error in the sliding window logic.

Author: byteduck

libraries/libgraphics/Framebuffer.cpp

@@ -126,80 +126,6 @@ void Framebuffer::copy_blitting(const Framebuffer& other, Rect other_area, const
 	}
 }
 
-void Framebuffer::blur(Gfx::Rect area, int radius) const {
-	int window_size = radius * 2 + 1;
-	area = area.overlapping_area(Rect{0, 0, width, height});
-
-	auto do_pass = [&]() {
-		// First, apply blur horizontally.
-		for(int y = area.y; y < area.y + area.height; y++) {
-			int window[3] = {0, 0, 0};
-			Color window_preblur[window_size];
-			int preblur_index = 0;
-
-			// Populate window
-			for(int i = -radius; i <= radius; i++) {
-				auto color = data[(std::min(std::max(area.x + i, 0), width - 1)) + y * width];
-				window_preblur[i + radius] = color;
-				window[0] += color.r;
-				window[1] += color.g;
-				window[2] += color.b;
-			}
-
-			for(int x = area.x; x < area.x + area.width; x++) {
-				data[x + y * width] = {
-						(uint8_t) (window[0] / window_size),
-						(uint8_t) (window[1] / window_size),
-						(uint8_t) (window[2] / window_size),
-				};
-				auto window_add = data[(std::min(x + radius + 1, width - 1)) + y * width];
-				auto window_sub = window_preblur[preblur_index];
-				window_preblur[preblur_index] = window_add;
-				preblur_index++;
-				preblur_index %= window_size;
-				window[0] += (int) window_add.r - (int) window_sub.r;
-				window[1] += (int) window_add.g - (int) window_sub.g;
-				window[2] += (int) window_add.b - (int) window_sub.b;
-			}
-		}
-
-		// Then, apply blur vertically.
-		for(int x = area.x; x < area.x + area.width; x++) {
-			int window[3] = {0, 0, 0};
-			Color window_preblur[window_size];
-			int preblur_index = 0;
-
-			// Populate window
-			for(int i = -radius; i <= radius; i++) {
-				auto color = data[x + (std::min(std::max(area.y + i, 0), height - 1)) * width];
-				window_preblur[i + radius] = color;
-				window[0] += color.r;
-				window[1] += color.g;
-				window[2] += color.b;
-			}
-
-			for(int y = area.y; y < area.y + area.height; y++) {
-				data[x + y * width] = {
-						(uint8_t) (window[0] / window_size),
-						(uint8_t) (window[1] / window_size),
-						(uint8_t) (window[2] / window_size),
-				};
-				auto window_add = data[x + (std::min(y + radius + 1, height - 1)) * width];
-				auto window_sub = window_preblur[preblur_index];
-				window_preblur[preblur_index] = window_add;
-				preblur_index++;
-				preblur_index %= window_size;
-				window[0] += (int) window_add.r - (int) window_sub.r;
-				window[1] += (int) window_add.g - (int) window_sub.g;
-				window[2] += (int) window_add.b - (int) window_sub.b;
-			}
-		}
-	};
-
-	for(int i = 0; i < 3; i++)
-		do_pass();
-}
-
 void Framebuffer::copy_blitting_flipped(const Framebuffer& other, Rect other_area, const Point& pos, bool flip_h, bool flip_v) const {
 	//Make sure self_area is in bounds of the framebuffer
 	Rect self_area = {pos.x, pos.y, other_area.width, other_area.height};
@@ -227,8 +153,9 @@ void Framebuffer::copy_blitting_flipped(const Framebuffer& other, Rect other_are
 
 void Framebuffer::blur(Gfx::Rect area, int radius) const {
 	int window_size = radius * 2 + 1;
+	area = area.overlapping_area(Rect {0, 0, width, height});
 
-	auto do_pass = [&]() { ;
+	auto do_pass = [&]() {
 		// First, apply blur horizontally.
 		for(int y = area.y; y < area.y + area.height; y++) {
 			int window[3] = {0, 0, 0};
@@ -250,11 +177,11 @@ void Framebuffer::blur(Gfx::Rect area, int radius) const {
 						(uint8_t) (window[1] / window_size),
 						(uint8_t) (window[2] / window_size),
 				};
-				auto window_add = data[(std::min(x + 5, width - 1)) + y * width];
+				auto window_add = data[(std::min(x + radius + 1, width - 1)) + y * width];
 				auto window_sub = window_preblur[preblur_index];
+				window_preblur[preblur_index] = window_add;
 				preblur_index++;
 				preblur_index %= window_size;
-				window_preblur[((preblur_index - 1) % window_size + window_size) % window_size] = window_add;
 				window[0] += (int) window_add.r - (int) window_sub.r;
 				window[1] += (int) window_add.g - (int) window_sub.g;
 				window[2] += (int) window_add.b - (int) window_sub.b;
@@ -269,7 +196,7 @@ void Framebuffer::blur(Gfx::Rect area, int radius) const {
 
 			// Populate window
 			for(int i = -radius; i <= radius; i++) {
-				auto color = data[(x + std::min(std::max(area.y + i, 0), height - 1)) * width];
+				auto color = data[x + (std::min(std::max(area.y + i, 0), height - 1)) * width];
 				window_preblur[i + radius] = color;
 				window[0] += color.r;
 				window[1] += color.g;
@@ -282,11 +209,11 @@ void Framebuffer::blur(Gfx::Rect area, int radius) const {
 						(uint8_t) (window[1] / window_size),
 						(uint8_t) (window[2] / window_size),
 				};
-				auto window_add = data[x + (std::min(y + 5, height - 1)) * width];
+				auto window_add = data[x + (std::min(y + radius + 1, height - 1)) * width];
 				auto window_sub = window_preblur[preblur_index];
+				window_preblur[preblur_index] = window_add;
 				preblur_index++;
 				preblur_index %= window_size;
-				window_preblur[((preblur_index - 1) % window_size + window_size) % window_size] = window_add;
 				window[0] += (int) window_add.r - (int) window_sub.r;
 				window[1] += (int) window_add.g - (int) window_sub.g;
 				window[2] += (int) window_add.b - (int) window_sub.b;

libraries/libgraphics/Framebuffer.h

@@ -76,13 +76,6 @@ namespace Gfx {
 		 */
 		void copy_blitting(const Framebuffer& other, Rect other_area, const Point& pos) const;
 
-		/**
-		 * Blurs an area of this framebuffer with an approximated gaussian blur.
-		 * @param area The area to blur.
-		 * @param radius The blur radius.
-		 */
-		void blur(Rect area, int radius = 4) const;
-
 		/**
 		 * Copies a part of another Image to this one, with alpha blending, flipped horizontally.
 		 * @param other The other Image to copy from.

services/pond/Window.h

@@ -269,17 +269,6 @@ class Window {
 	 */
 	bool blurs_behind() const;
 
-	/**
-	 * Gets the shadow framebuffers for drawing shadows.
-	 * Sets whether the window should blur contents behind it.
-	 */
-	void set_blur_behind(bool blur);
-
-	/**
-	 * Returns whether the window blurs contents behind it.
-	 */
-	bool blurs_behind() const;
-
 	/**
 	 * Gets the shadow framebuffer for drawing shadows.
 	 */