feat(asyguide): IMO 1974/4 figure

input/asyguide.md

@@ -24,6 +24,7 @@ You can [view the source code on GitHub][asy-gallery].
 {{ clickable_asy_image("321avoid") }}
 {{ clickable_asy_image("AMC-12B-2022-21") }}
 {{ clickable_asy_image("EGMO-2015-2") }}
+{{ clickable_asy_image("IMO-1974-4") }}
 {{ clickable_asy_image("IMO-2017-5") }}
 {{ clickable_asy_image("Jan-TST-2013-3") }}
 {{ clickable_asy_image("Mexico-2020-3") }}

static/asy-gallery/IMO-1974-4.asy

@@ -0,0 +1,73 @@
+size(13cm);
+picture g;
+for (int i=0; i<8; ++i) {
+  for (int j=0; j<8; ++j) {
+    if ((i+j)%2 == 0) {
+      fill(g, shift(i,j)*unitsquare, rgb("cccccc"));
+    }
+  }
+}
+
+picture p1, p2, p3, p4;
+add(p1, g);
+add(p2, g);
+add(p3, g);
+add(p4, g);
+label(p1, "$64 = 2 + 4 + 6 + 10 + 12 + 14 + 16$", (4,0), dir(-90));
+label(p2, "$64 = 2 + 4 + 6 + 8 + 12 + 14 + 18$", (4,0), dir(-90));
+label(p3, "$64 = 2 + 4 + 6 + 8 + 10 + 16 + 18$", (4,0), dir(-90));
+label(p4, "$64 = 2 + 4 + 6 + 8 + 10 + 14 + 20$", (4,0), dir(-90));
+
+pen r = heavyred+1.4+fontsize(16pt);
+pen[] colors = {
+  green, orange, yellow, blue, purple,
+  lightred, cyan, darkcyan, olive, fuchsia
+};
+void draw_rect(picture p, int x1, int y1, int x2, int y2) {
+  int a = abs((y2-y1)*(x2-x1));
+  filldraw(p, box((x1,y1),(x2,y2)), opacity(0.2)+colors[a#2-1], r);
+  label(p, "\textbf{" + (string) a + "}", ((x1+x2)/2, (y1+y2)/2), r);
+}
+draw_rect(p1, 0,6, 1,8);
+draw_rect(p1, 1,6, 8,8);
+draw_rect(p1, 0,4, 2,6);
+draw_rect(p1, 2,4, 8,6);
+draw_rect(p1, 0,2, 3,4);
+draw_rect(p1, 3,2, 8,4);
+draw_rect(p1, 0,0, 8,2);
+
+draw_rect(p2, 0,6, 1,8);
+draw_rect(p2, 1,6, 8,8);
+draw_rect(p2, 0,4, 2,6);
+draw_rect(p2, 2,4, 8,6);
+draw_rect(p2, 0,1, 2,4);
+draw_rect(p2, 2,1, 8,4);
+draw_rect(p2, 0,0, 8,1);
+
+draw_rect(p3, 0,6, 1,8);
+draw_rect(p3, 1,6, 3,8);
+draw_rect(p3, 3,6, 8,8);
+draw_rect(p3, 0,4, 8,6);
+draw_rect(p3, 0,1, 2,4);
+draw_rect(p3, 2,1, 8,4);
+draw_rect(p3, 0,0, 8,1);
+
+draw_rect(p4, 0,6, 1,8);
+draw_rect(p4, 1,6, 8,8);
+draw_rect(p4, 2,1, 4,6);
+draw_rect(p4, 0,4, 2,6);
+draw_rect(p4, 0,1, 2,4);
+draw_rect(p4, 4,1, 8,6);
+draw_rect(p4, 0,0, 8,1);
+
+pen border = black+1.5;
+draw(p1, box((0,0), (8,8)), border);
+draw(p2, box((0,0), (8,8)), border);
+draw(p3, box((0,0), (8,8)), border);
+draw(p4, box((0,0), (8,8)), border);
+
+real w = 9.5;
+add(shift(0,0)*p1);
+add(shift(w,0)*p2);
+add(shift(0,-w)*p3);
+add(shift(w,-w)*p4);