Snowy with Fog style image processor (a function)

Converts an image to a snowy fog style with realistic Bokeh flakes.

function imgOut = snowyFog(inputData, varargin)

% snowyFog_v4: Converts an image to a snowy fog style with realistic Bokeh flakes.

% 将图像转换为雪雾风格，雪花效果基于真实的焦外成像(Bokeh)原理。

%

% Version: 4.0 (Bugfix & Blend Mode Improvement)

% Key Improvements:

% - Fixed a critical bug that caused the image to turn white.

% (修复了导致画面全白的致命bug)

% - Used Screen Blend for layering snowflakes, preventing brightness overflow.

% (使用屏幕混合模式叠加雪花，防止亮度溢出，效果更真实)

%

% USAGE:

% imshow(snowyFog('landscape.jpg'));

% imgOut = snowyFog(img, 'snow_amount', 20000, 'flake_blur_range', [0.5, 8]);

% 1. Input Parser / 参数解析

p = inputParser;

addRequired(p, 'inputData');

addParameter(p, 'fog_density', 0.6, @(x) x>=0 && x<=1);

addParameter(p, 'snow_amount', 1500, @isnumeric);

addParameter(p, 'motion_blur_strength', 20, @isnumeric);

addParameter(p, 'desaturation', 0.8, @(x) x>=0 && x<=1);

addParameter(p, 'flake_blur_range', [5, 20], @(x) isnumeric(x) && numel(x)==2); % [min_sigma, max_sigma]

addParameter(p, 'flake_opacity_range', [10, 50], @(x) isnumeric(x) && numel(x)==2); % [min, max]

parse(p, inputData, varargin{:});

params = p.Results;

% 2. Load Image & Initialization / 读取图像与初始化

if ischar(params.inputData) || isstring(params.inputData)

img_orig = imread(params.inputData);

else if isnumeric(params.inputData) && ndims(params.inputData) == 3

img_orig = params.inputData;

else, error('Invalid input. Must be a file path or an RGB image matrix.');

end

end

img_orig = im2double(img_orig);

[h, w, ~] = size(img_orig);

fprintf('Initializing snowy fog effect v4.0 (Bugfix Edition)...\n');

% 3. Layer 1: Depth-Aware Fog / 第一层: 带景深的雾气

fprintf('Layer 1: Generating depth-aware fog...\n');

gray_img = rgb2gray(img_orig);

desaturated_img = gray_img * params.desaturation + img_orig * (1 - params.desaturation);

depth_mask = repmat(linspace(1, 0.2, h)', 1, w);

depth_mask = imgaussfilt(depth_mask, 20);

fog_intensity = depth_mask .* params.fog_density;

fog_color = 0.95;

foggy_img = desaturated_img .* (1 - fog_intensity) + fog_color .* fog_intensity;

foggy_img = imgaussfilt(foggy_img, 1.5);

foggy_img = min(max(foggy_img, 0), 1);

% 4. Layer 2: Randomized Bokeh Snowflakes / 第二层: 随机焦外成像雪花

fprintf('Layer 2: Generating realistic Bokeh snowflakes...\n');

num_flakes = params.snow_amount;

x_coords = randi(w, num_flakes, 1);

y_coords = randi(h, num_flakes, 1);

flake_sigmas = params.flake_blur_range(1) + rand(num_flakes, 1) * (params.flake_blur_range(2) - params.flake_blur_range(1));

flake_opacities = params.flake_opacity_range(1) + rand(num_flakes, 1) * (params.flake_opacity_range(2) - params.flake_opacity_range(1));

num_groups = 6;

sigma_groups = linspace(params.flake_blur_range(1), params.flake_blur_range(2), num_groups);

snow_canvas = zeros(h, w);

screen_blend = @(A, B) 1 - (1 - A) .* (1 - B); % 定义屏幕混合函数

for i = 1:num_groups

if i == 1

indices = flake_sigmas <= sigma_groups(1);

else

indices = flake_sigmas > sigma_groups(i-1) & flake_sigmas <= sigma_groups(i);

end

if ~any(indices), continue; end

group_x = x_coords(indices);

group_y = y_coords(indices);

group_opacities = flake_opacities(indices);

temp_canvas = zeros(h, w);

linear_indices = sub2ind([h, w], group_y, group_x);

temp_canvas(linear_indices) = group_opacities;

kernel_sigma = mean(flake_sigmas(indices));

if kernel_sigma > 0.1

kernel_size = ceil(kernel_sigma * 6) + 1;

kernel = fspecial('gaussian', kernel_size, kernel_sigma);

temp_canvas = imfilter(temp_canvas, kernel, 'replicate', 'conv');

end

% --- 【核心修正】---

% 使用屏幕混合模式叠加雪花层，而不是简单相加(+)，以防止亮度溢出

snow_canvas = screen_blend(snow_canvas, temp_canvas);

end

% --- 【修正】移除了之前版本中错误的clamping操作 ---

% The line 'snow_canvas = min(max(snow_canvas, 1), 1);' has been removed.

% 'screen_blend' naturally handles the brightness, making the clamp unnecessary.

% 屏幕混合模式自然地处理了亮度，不再需要手动限制。

if params.motion_blur_strength > 0

angle = 90 + (rand-0.5)*20;

motion_kernel = fspecial('motion', params.motion_blur_strength, angle);

snow_canvas = imfilter(snow_canvas, motion_kernel, 'replicate', 'conv');

end

snow_canvas_color = repmat(snow_canvas, [1, 1, 3]);

% 5. Final Blending / 最终混合

fprintf('Finalizing the image...\n');

final_img = screen_blend(foggy_img, snow_canvas_color);

% 6. Final Output / 最终输出

imgOut = im2uint8(final_img);

fprintf('Snowy fog effect v4.0 applied successfully.\n');

end