Util: Add mPainterDrawCircle

include/mgba-util/image.h

@@ -137,6 +137,7 @@ void mImageCompositeWithAlpha(struct mImage* image, const struct mImage* source,
 void mPainterInit(struct mPainter*, struct mImage* backing);
 void mPainterDrawRectangle(struct mPainter*, int x, int y, int width, int height);
 void mPainterDrawLine(struct mPainter*, int x1, int y1, int x2, int y2);
+void mPainterDrawCircle(struct mPainter*, int x, int y, int diameter);
 
 uint32_t mColorConvert(uint32_t color, enum mColorFormat from, enum mColorFormat to);
 uint32_t mImageColorConvert(uint32_t color, const struct mImage* from, enum mColorFormat to);

src/util/image.c

@@ -557,6 +557,13 @@ void mPainterInit(struct mPainter* painter, struct mImage* backing) {
 	painter->backing = backing;
 }
 
+static void mPainterDrawPixel(struct mPainter* painter, unsigned x, unsigned y, uint32_t color) {
+	if (painter->blend) {
+		color = mColorMixARGB8(painter->strokeColor, mImageGetPixel(painter->backing, x, y));
+	}
+	mImageSetPixel(painter->backing, x, y, color);
+}
+
 static void mPainterFillRectangle(struct mPainter* painter, int x, int y, int width, int height) {
 	FILL_BOUNDS_INIT(x, y, width, height);
 
@@ -651,10 +658,7 @@ void mPainterDrawLine(struct mPainter* painter, int x1, int y1, int x2, int y2)
 		y = y1;
 		for (x = x1; x != x2 + xi; x += xi) {
 			for (i = 0; i < painter->strokeWidth; ++i) {
-				if (painter->blend) {
+				mPainterDrawPixel(painter, x, y - painter->strokeWidth / 2 + i, color);
-					color = mColorMixARGB8(painter->strokeColor, mImageGetPixel(painter->backing, x, y - painter->strokeWidth / 2 + i));
-				}
-				mImageSetPixel(painter->backing, x, y - painter->strokeWidth / 2 + i, color);
 			}
 			if (residual > 0) {
 				y += yi;
@@ -667,10 +671,7 @@ void mPainterDrawLine(struct mPainter* painter, int x1, int y1, int x2, int y2)
 		x = x1;
 		for (y = y1; y != y2 + yi; y += yi) {
 			for (i = 0; i < painter->strokeWidth; ++i) {
-				if (painter->blend) {
+				mPainterDrawPixel(painter, x - painter->strokeWidth / 2 + i, y, color);
-					color = mColorMixARGB8(painter->strokeColor, mImageGetPixel(painter->backing, x - painter->strokeWidth / 2 + i, y));
-				}
-				mImageSetPixel(painter->backing, x - painter->strokeWidth / 2 + i, y, color);
 			}
 			if (residual > 0) {
 				x += xi;
@@ -683,6 +684,133 @@ void mPainterDrawLine(struct mPainter* painter, int x1, int y1, int x2, int y2)
 	// TODO: Draw endcaps for widths >2
 }
 
+static void _drawCircleOctants(struct mPainter* painter, int x, int y, int offx, int offy, int offset, uint32_t color) {
+	mPainterDrawPixel(painter, x + offy - offset, y + offx - offset, color);
+	mPainterDrawPixel(painter, x - offy, y + offx - offset, color);
+	mPainterDrawPixel(painter, x + offy - offset, y - offx, color);
+	mPainterDrawPixel(painter, x - offy, y - offx, color);
+	if (offx < offy) {
+		mPainterDrawPixel(painter, x + offx - offset, y + offy - offset, color);
+		mPainterDrawPixel(painter, x - offx, y + offy - offset, color);
+		mPainterDrawPixel(painter, x + offx - offset, y - offy, color);
+		mPainterDrawPixel(painter, x - offx, y - offy, color);
+	}
+}
+
+static void _drawCircle2x2(struct mPainter* painter, int x, int y, uint32_t color) {
+	mPainterDrawPixel(painter, x, y, color);
+	mPainterDrawPixel(painter, x - 1, y, color);
+	mPainterDrawPixel(painter, x, y - 1, color);
+	mPainterDrawPixel(painter, x - 1, y - 1, color);
+}
+
+void mPainterDrawCircle(struct mPainter* painter, int x, int y, int diameter) {
+	int radius = diameter / 2;
+	int offset = (diameter ^ 1) & 1;
+	int stroke = painter->strokeWidth;
+	int dx = 1;
+	int residual0 = 1 - radius;
+	int dy0 = -2 * radius;
+	int offx = 0;
+	int offy;
+	int y0 = radius;
+	if (stroke > radius) {
+		// Clamp stroke
+		stroke = radius;
+		if (!offset) {
+			// Draw center dot as stroke
+			mPainterDrawPixel(painter, x + radius, y + radius, painter->strokeColor);
+		}
+	} else if (!offset && painter->fill) {
+		// Draw center dot as fill
+		mPainterDrawPixel(painter, x + radius, y + radius, painter->fillColor);
+	}
+
+	int residual1 = 1 - radius + stroke;
+	int dy1 = -2 * (radius - stroke);
+	int y1 = radius - stroke;
+	int i;
+
+	if (!offset) {
+		// Draw central axes
+		for (i = 0; i < stroke; ++i) {
+			mPainterDrawPixel(painter, x + radius, y + radius * 2 - i, painter->strokeColor);
+			mPainterDrawPixel(painter, x + radius, y + i, painter->strokeColor);
+			mPainterDrawPixel(painter, x + radius * 2 - i, y + radius, painter->strokeColor);
+			mPainterDrawPixel(painter, x + i, y + radius, painter->strokeColor);
+		}
+		if (painter->fill) {
+			for (i = i; i < y1 + 1; ++i) {
+				mPainterDrawPixel(painter, x + radius, y + radius - i, painter->fillColor);
+				mPainterDrawPixel(painter, x + radius, y + radius + i, painter->fillColor);
+				mPainterDrawPixel(painter, x + radius - i, y + radius, painter->fillColor);
+				mPainterDrawPixel(painter, x + radius + i, y + radius, painter->fillColor);
+			}
+		}
+	}
+
+	while (offx < y0) {
+		if (residual0 >= 0) {
+			y0 -= 1;
+			dy0 += 2;
+			residual0 += dy0;
+		}
+		if (residual1 >= 0) {
+			y1 -= 1;
+			dy1 += 2;
+			residual1 += dy1;
+		}
+		offx += 1;
+		dx += 2;
+		residual0 += dx;
+		residual1 += dx;
+		if (stroke) {
+			// Fill
+			if (painter->fill) {
+				if (offx == 1 && y1 == 0 && offset) {
+					// Special case for diameter-2 fill
+					_drawCircle2x2(painter, x + radius, y + radius, painter->fillColor);
+				} else {
+					for (offy = 0; offy < y1 + 1; ++offy) {
+						if (offx > offy) {
+							continue;
+						}
+						_drawCircleOctants(painter, x + radius, y + radius, offx, offy, offset, painter->fillColor);
+					}
+				}
+			}
+			// Stroke
+			if (radius == 1 && offset) {
+				// Special case for diameter-2 stroke
+				_drawCircle2x2(painter, x + radius, y + radius, painter->strokeColor);
+			} else {
+				for (offy = y1 + 1; offy < y0 + 1; ++offy) {
+					if (offx == 1 && offy == 1 && y1 == 0 && offset) {
+						// Special case for diameter-2 inner fill
+						continue;
+					}
+					if (offx > offy) {
+						continue;
+					}
+					_drawCircleOctants(painter, x + radius, y + radius, offx, offy, offset, painter->strokeColor);
+				}
+			}
+		} else if (painter->fill) {
+			if (offx == 1 && y0 == 0 && offset) {
+				// Special case for diameter-2 fill
+				_drawCircle2x2(painter, x, y, painter->fillColor);
+			} else {
+				for (offy = 0; offy < y0 + 1; ++offy) {
+					if (offx > offy) {
+						continue;
+					}
+					_drawCircleOctants(painter, x + radius, y + radius, offx, offy, offset, painter->fillColor);
+				}
+			}
+		}
+	}
+}
+
 uint32_t mColorConvert(uint32_t color, enum mColorFormat from, enum mColorFormat to) {
 	if (from == to) {
 		return color;

src/util/test/image.c

@@ -1849,6 +1849,95 @@ M_TEST_DEFINE(painterDrawLineBlend) {
 	mImageDestroy(image);
 }
 
+M_TEST_DEFINE(painterDrawCircleArea) {
+	struct mImage* image;
+	struct mPainter painter;
+
+	int i;
+	for (i = 4; i < 50; ++i) {
+		image = mImageCreate(i, i, mCOLOR_XRGB8);
+		mPainterInit(&painter, image);
+		painter.blend = false;
+		painter.fill = true;
+		painter.strokeWidth = 0;
+		painter.fillColor = 0xFF0000FF;
+		mPainterDrawCircle(&painter, 0, 0, i);
+
+		int filled = 0;
+
+		int x, y;
+		for (y = 0; y < i; ++y) {
+			for (x = 0; x < i; ++x) {
+				uint32_t color = mImageGetPixel(image, x, y);
+				if (color == painter.fillColor) {
+					++filled;
+				}
+			}
+		}
+		float area = i * i;
+		assert_float_equal(filled / area, M_PI / 4, 0.12);
+	}
+}
+
+M_TEST_DEFINE(painterDrawCircleCircumference) {
+	struct mImage* image;
+	struct mPainter painter;
+
+	int i;
+	for (i = 25; i < 100; ++i) {
+		image = mImageCreate(i, i, mCOLOR_XRGB8);
+		mPainterInit(&painter, image);
+		painter.blend = false;
+		painter.fill = false;
+		painter.strokeWidth = 1;
+		painter.strokeColor = 0xFF0000FF;
+		mPainterDrawCircle(&painter, 0, 0, i);
+
+		int filled = 0;
+
+		int x, y;
+		for (y = 0; y < i; ++y) {
+			for (x = 0; x < i; ++x) {
+				uint32_t color = mImageGetPixel(image, x, y);
+				if (color == painter.strokeColor) {
+					++filled;
+				}
+			}
+		}
+		assert_float_equal(filled / (float) i, M_PI, M_PI * 0.11);
+	}
+}
+
+
+M_TEST_DEFINE(painterDrawCircleOffset) {
+	struct mImage* image;
+	struct mPainter painter;
+
+	int i;
+	for (i = 4; i < 20; ++i) {
+		image = mImageCreate(i * 2, i * 2, mCOLOR_XRGB8);
+		mPainterInit(&painter, image);
+		painter.blend = false;
+		painter.fill = true;
+		painter.strokeWidth = 0;
+		painter.fillColor = 0xFF0000FF;
+		mPainterDrawCircle(&painter, 0, 0, i);
+		mPainterDrawCircle(&painter, i, 0, i);
+		mPainterDrawCircle(&painter, 0, i, i);
+		mPainterDrawCircle(&painter, i, i, i);
+
+		int x, y;
+		for (y = 0; y < i; ++y) {
+			for (x = 0; x < i; ++x) {
+				uint32_t color = mImageGetPixel(image, x, y);
+				assert_int_equal(color, mImageGetPixel(image, x + i, y));
+				assert_int_equal(color, mImageGetPixel(image, x, y + i));
+				assert_int_equal(color, mImageGetPixel(image, x + i, y + i));
+			}
+		}
+	}
+}
+
 #undef COMPARE3X
 #undef COMPARE3
 #undef COMPARE4X
@@ -1887,4 +1976,7 @@ M_TEST_SUITE_DEFINE(Image,
 	cmocka_unit_test(painterDrawLineOctants),
 	cmocka_unit_test(painterDrawLineWidth),
 	cmocka_unit_test(painterDrawLineBlend),
+	cmocka_unit_test(painterDrawCircleArea),
+	cmocka_unit_test(painterDrawCircleCircumference),
+	cmocka_unit_test(painterDrawCircleOffset),
 )