Add preliminar version of integral image

bfactory-ai · Apr 25, 2024 · 522c5aa · 522c5aa
1 parent 149bed1
commit 522c5aa
Show file tree

Hide file tree

Showing 2 changed files with 63 additions and 0 deletions.
diff --git a/src/image.zig b/src/image.zig
@@ -2,6 +2,8 @@ const std = @import("std");
 const Allocator = std.mem.Allocator;
 const Rgba = @import("color.zig").Rgba;
 const as = @import("meta.zig").as;
+const isScalar = @import("meta.zig").isScalar;
+const isStruct = @import("meta.zig").isStruct;
 const Rectangle = @import("geometry.zig").Rectangle(f32);
 const Point2d = @import("point.zig").Point2d(f32);
 
@@ -152,5 +154,50 @@ pub fn Image(comptime T: type) type {
             }
             return chip;
         }
+
+        pub fn computeIntegralImage(self: Self, allocator: Allocator) if (isScalar(T)) Image(f32) else if (isStruct(T)) Image([std.meta.fields(T).len]f32) else @compileError("Can't compute the integral image of " ++ @typeName(T) ++ ".") {
+            switch (@typeInfo(T)) {
+                .ComptimeInt, .Int, .ComptimeFloat, .Float => {
+                    var integral = Image(f32).initAlloc(allocator, self.rows, self.cols);
+                    var tmp: f32 = 0;
+                    for (0..self.cols) |c| {
+                        tmp += as(f32, (self.data[c]));
+                        integral.data[c] = tmp;
+                    }
+                    for (1..self.rows) |r| {
+                        tmp = 0;
+                        for (0..self.cols) |c| {
+                            const curr_pos = r * self.cols + c;
+                            const prev_pos = (r - 1) * self.cols + c;
+                            tmp += as(f32, self.data[curr_pos]);
+                            integral.data[curr_pos] = tmp + integral.data[prev_pos];
+                        }
+                    }
+                    return integral;
+                },
+                .Struct => {
+                    const num_fields = std.meta.fields(T).len;
+                    var integral = Image([num_fields]f32).initAlloc(self.rows, self.cols);
+                    inline for (std.meta.fields(T), 0..) |f, i| {
+                        var tmp: f32 = 0;
+                        for (0..self.cols) |c| {
+                            tmp[i] += as(f32, @field(self, f.name));
+                            integral.data[c][i] = tmp[i];
+                        }
+                        for (1..self.rows) |r| {
+                            tmp = 0;
+                            for (0..self.cols) |c| {
+                                const curr_pos = r * self.cols + c;
+                                const prev_pos = (r - 1) * self.cols + c;
+                                tmp += as(f32, self.data[curr_pos][i]);
+                                integral.data[curr_pos][i] = tmp + integral.data[prev_pos][i];
+                            }
+                        }
+                    }
+                    return integral;
+                },
+                else => @compileError("Can't compute the integral image of " ++ @typeName(T) ++ "."),
+            }
+        }
     };
 }
diff --git a/src/meta.zig b/src/meta.zig
@@ -25,3 +25,19 @@ pub inline fn as(comptime T: type, from: anytype) T {
         else => @compileError(@typeName(@TypeOf(from) ++ " is not supported.")),
     }
 }
+
+/// Returns true if and only if T represents a scalar type.
+pub inline fn isScalar(comptime T: type) bool {
+    return switch (@typeInfo(T)) {
+        .ComptimeInt, .Int, .ComptimeFloat, .Float => true,
+        else => false,
+    };
+}
+
+/// Returns true if and only if T represents a struct type.
+pub inline fn isStruct(comptime T: type) bool {
+    return switch (@typeInfo(T)) {
+        .Struct => true,
+        else => false,
+    };
+}