Add tool to build random scenes.

Add utility functions for channel extraction.

build_scene.m

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+function [scene, target] = build_scene(file, num_anomalies)
+%BUILD_SCENE Reads image file and adds anomalies to it.
+%   Returns image and target map showing anomalies. Anomalies are luminance
+%   adjusted to match the surroundings. Defaults to 3 anomalies.
+
+if nargin < 2
+    num_anomalies = 3;
+end
+
+% settings
+desired_width = 1536;
+anomaly_height = 10; % all anomalies are normalized to 100 high, so use height as normalizing factor
+
+% read a scene
+scene = imread(['scenes/' file]);
+scene = normalize_image(imresize(scene, [nan desired_width]));
+
+% make target
+target = false(size(scene, 1), size(scene, 2));
+
+% anomaly files
+anomaly_files = dir('anomalies/*.png');
+anomaly_files = {anomaly_files.name};
+perm = randperm(length(anomaly_files));
+anomaly_files = anomaly_files(perm);
+
+% scene luminance information
+scene_luminance = rgb2lab(scene);
+scene_luminance = scene_luminance(:, :, 1);
+
+for j = 1:num_anomalies
+    % read an anomaly
+    [anom, ~, anom_mask] = imread(['anomalies/' anomaly_files{j}]);
+
+    % resize
+    anom = imresize(anom, [anomaly_height nan]);
+    anom_mask = imresize(anom_mask, [anomaly_height nan]);
+
+    % rotate
+    ang = rand * 365;
+    anom = normalize_image(imrotate(anom, ang, 'bicubic'));
+    anom_mask = imrotate(anom_mask, ang, 'bilinear');
+
+    % figure out threshold for alpha (want enough of the anomaly, but not grain edges)
+    th = 255;
+    while sum(sum(anom_mask >= th)) < (0.5 * anomaly_height * anomaly_height)
+        th = th - 5;
+    end
+
+    % position
+    pos = rand(1, 3) .* (size(scene) - size(anom));
+    pos = round(pos(1:2));
+
+    % average luminance
+    med_y_scene = median(median(scene_luminance(pos(1):pos(1) + size(anom, 1) - 1, pos(2):pos(2) + size(anom, 2) - 1)));
+
+    % adjust luminance
+    anom = rgb2lab(anom);
+    anom_y = anom(:, :, 1);
+    med_y_anom = median(median(anom_y(anom_mask >= th)));
+    anom(:, :, 1) = anom_y * (med_y_scene / med_y_anom);
+    anom = lab2rgb(anom);
+
+    % build mask for all channels
+    single_mask = (anom_mask >= th);
+    mask = single_mask;
+    while size(mask, 3) < size(scene, 3)
+        mask = cat(3, mask, single_mask);
+    end
+
+    % local scene
+    scene_local = scene(pos(1):pos(1) + size(anom, 1) - 1, pos(2):pos(2) + size(anom, 2) - 1, :);
+    % replace channels
+    scene_local(mask) = anom(mask);
+    scene(pos(1):pos(1) + size(anom, 1) - 1, pos(2):pos(2) + size(anom, 2) - 1, :) = scene_local;
+
+    % update target
+    target(pos(1):pos(1) + size(anom, 1) - 1, pos(2):pos(2) + size(anom, 2) - 1) = target(pos(1):pos(1) + size(anom, 1) - 1, pos(2):pos(2) + size(anom, 2) - 1) | single_mask;
+end
+
+end
+

select_channel.m

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+function img_ss = select_channel(img, channels)
+%SELECT_CHANNEL Select specific channel(s).
+img_ss = img(:, :, channels);
+end
+

transform_channel.m

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+function img_tc = transform_channel(img, channel, cb)
+%TRANSFORM_CHANNEL Apply callback to channel(s).
+img_tc = img;
+img_tc(:, :, channel) = cb(img_tc(:, :, channel));
+end
+