├── .gitignore ├── COPYING ├── README.md ├── colour_pencil_draw.m ├── download_to_all.rb ├── draw_all.m ├── gaussian_filter.m ├── horizontal_stitch.m ├── img ├── flower.png └── sign.png ├── natural_histogram_matching.m ├── npar12_pencil.pdf ├── pencil_draw.m ├── textures ├── a.jpg ├── d.jpg └── texture.jpg ├── vertical_stitch.m └── ycbcr2rgb.m /.gitignore: -------------------------------------------------------------------------------- 1 | tmp/ 2 | *.swp 3 | *.m~ 4 | -------------------------------------------------------------------------------- /COPYING: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Pencil 2 | implementation of http://www.cse.cuhk.edu.hk/~leojia/projects/pencilsketch/pencil_drawing.htm 3 | 4 | ## Usage 5 | * black and white: `imshow(pencil_draw(imread('photo.jpg')));` 6 | * colour pencil drawing: `imshow(colour_pencil_draw(imread('photo.jpg')));` 7 | * to draw all files in a folder please see draw_all.m 8 | 9 | ## Demo 10 | https://fumin.github.io/future-graphics 11 | 12 | ## License 13 | Copyright 2013 Awaw Fumin awawfumin@gmail.com 14 | Licensed under GNU General Public License v3 15 | 16 | ## Todos 17 | * coloured outline sketches 18 | -------------------------------------------------------------------------------- /colour_pencil_draw.m: -------------------------------------------------------------------------------- 1 | function R = colour_pencil_draw(I) 2 | % Usage: imshow(colour_pencil_draw(imread('img/sign.png'))) 3 | Iruv = rgb2ycbcr(I); 4 | Ypencil = pencil_draw(Iruv(:,:,1)); 5 | 6 | new_Iruv = Iruv; 7 | new_Iruv(:,:,1) = uint8(Ypencil*255); 8 | R = ycbcr2rgb(new_Iruv); -------------------------------------------------------------------------------- /download_to_all.rb: -------------------------------------------------------------------------------- 1 | require 'net/http' 2 | require 'uri' 3 | 4 | urls_file = 'tmp/urls' 5 | dest_dir = 'tmp/all' 6 | urls = File.read(urls_file).split("\n") 7 | 8 | urls.each do |url| 9 | extname = /(\.\w+$)/.match(url)[1] 10 | random_str = rand(2**256).to_s(36).ljust(8,'a')[0..7] 11 | File.open(dest_dir + '/' + random_str + extname, 'wb') do |f| 12 | f.write Net::HTTP.get(URI(url)) 13 | end 14 | puts "#{url} OK" 15 | end 16 | -------------------------------------------------------------------------------- /draw_all.m: -------------------------------------------------------------------------------- 1 | pkg load image 2 | files = dir('tmp/all/*.jpg'); 3 | for d=1:length(files) 4 | file_name = fullfile('tmp/all', files(d).name); 5 | fprintf('%s\n', file_name); 6 | I = imread(file_name); 7 | max_wh = max(size(I)); 8 | if max_wh > 1024 9 | I = imresize(I, 1024/max_wh); 10 | end 11 | 12 | b = pencil_draw(I); 13 | R = colour_pencil_draw(I); 14 | imwrite(b, strcat('pencil_',files(d).name), 'jpg'); 15 | imwrite(R, strcat('colour_',files(d).name), 'jpg'); 16 | end 17 | -------------------------------------------------------------------------------- /gaussian_filter.m: -------------------------------------------------------------------------------- 1 | function Igaussian = gaussian_filter(I, sigma) 2 | hsize = 3*round(sigma); 3 | h = zeros(hsize); 4 | for i=1:hsize 5 | for j=1:hsize 6 | u = [j-(3*sigma)/2, i-(3*sigma)/2]; 7 | h(i,j) = exp(-u*u'/(2*sigma*sigma))/sigma*sqrt(2*pi); 8 | end 9 | end 10 | 11 | Igaussian = conv2(I, h, 'same'); 12 | Igaussian = Igaussian / max(max(Igaussian)); -------------------------------------------------------------------------------- /horizontal_stitch.m: -------------------------------------------------------------------------------- 1 | function Istitched = horizontal_stitch(I,width) 2 | % Continuously repeat the image I horizontally until the width of the 3 | % resulting image is 'width'. 4 | % We use alpha blending to smooth the borders in the replication 5 | % 6 | % I must be within 0 and 1 7 | Istitched = I; 8 | while size(Istitched,2)= 0 57 | res = x 58 | else 59 | res = 0 60 | end 61 | end 62 | -------------------------------------------------------------------------------- /npar12_pencil.pdf: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/fumin/pencil/31c5fd8cf4112e17592db5be1acf39aa8670e074/npar12_pencil.pdf -------------------------------------------------------------------------------- /pencil_draw.m: -------------------------------------------------------------------------------- 1 | function Ipencil = pencil_draw(I) 2 | % The algorithm is as follows: 3 | % 1. Compute the outline sketch 'S' 4 | % * Prepare the 8 directional line segment images, 'L', 5 | % all with width and height 'line_len', which is around 1/30 of the 6 | % input image I's width 7 | % * Compute the gradient of the input image which is 'Imag' 8 | % * Generate the pixel classification 'C' of the 8 directions 9 | % * Convolute the 8 'C's and 'L's to obtain our final outline sketch 'S' 10 | % 2. Compute the texture tone drawing 'T' 11 | % * Prepare 'Jadjusted' which is the adjusted the raw image 'J' 12 | % against the natural histogram of typical pencil drawings. 13 | % * Repetitively stitch our base texture image to the size of our raw image. 14 | % The result is 'Jtexture', our base texture background. 15 | % * Solve for 'beta', the number of times we should draw the texture. 16 | % 'beta' should have the same width and height as our raw image 'J': 17 | % * Although beta is two dimensional, see it as an 18 | % one dimensional column 'b' with length size(J,1)*size(J,2). 19 | % The same goes for 'Jadjusted', whose one dimensional column 20 | % representation is 'Ja'. 21 | % * Our minimization objective function is: 22 | % |log(Jtexture_diag)*b - log(Ja)|^2 + lambda*(|dx*b|^2+|dy*b|^2) 23 | % Where 'Jtexture_diag' is a diagonal square matrix whose 24 | % width equals the length of 'b' and with 25 | % Jtexture's column representation at its diagonals. 26 | % 'dx' and 'dy' are square matrices that represent 27 | % image pixel differences at the x and y directions. 28 | % * Apparently, 'Jtexture_diag', 'dx' and 'dy' are all matrices 29 | % of extreme size, therefore they should be sparse matrices. 30 | % * Our desired texture tone drawing 'T' is Jtexture.^beta 31 | % 3. Combine 'S' and 'T' 32 | % 33 | % Usage: imshow(pencil_draw(imread('img/sign.png'))) 34 | % Constants: 35 | line_len_divisor = 40; % larger for a shorter line fragment 36 | line_thickness_divisor = 8; % larger for thiner outline sketches 37 | lambda = 2; % larger for smoother tonal mappings 38 | texture_resize_ratio = 0.2; 39 | texture_file_name = 'textures/texture.jpg'; 40 | 41 | if length(size(I)) == 3 42 | J = rgb2gray(I); 43 | type = 'black'; 44 | else 45 | J = I; 46 | type = 'colour'; 47 | end 48 | 49 | % ================================================ 50 | % Compute the outline sketch 'S' 51 | % ================================================ 52 | % calculate 'line_len', the length of the line segments 53 | line_len_double = min([size(J,1), size(J,2)]) / line_len_divisor; 54 | if mod(floor(line_len_double), 2) 55 | line_len = floor(line_len_double); 56 | else 57 | line_len = floor(line_len_double) + 1; 58 | end 59 | half_line_len = (line_len + 1) / 2; 60 | 61 | % compute the image gradient 'Imag' 62 | Ix = conv2(im2double(J), [1,-1;1,-1], 'same'); 63 | Iy = conv2(im2double(J), [1,1;-1,-1], 'same'); 64 | Imag = sqrt(Ix.*Ix + Iy.*Iy); 65 | 66 | % create the 8 directional line segments L 67 | L = zeros(line_len, line_len, 8); 68 | for n=0:7 69 | if n == 0 || n == 1 || n == 2 || n == 7 70 | for x=1:line_len 71 | y = half_line_len - round((x-half_line_len)*tan(pi/8*n)); 72 | if y > 0 && y <= line_len 73 | L(y, x, n+1) = 1; 74 | end 75 | end 76 | if n == 0 || n == 1 || n == 2 77 | L(:,:,n+5) = rot90(L(:,:,n+1)); 78 | end 79 | end 80 | end 81 | L(:,:,4) = rot90(L(:,:,8), 3); 82 | 83 | % add some thickness to L 84 | valid_width = size(conv2(L(:,:,1),ones(round(line_len/line_thickness_divisor)),'valid'), 1); 85 | Lthick = zeros(valid_width, valid_width, 8); 86 | for n=1:8 87 | Ln = conv2(L(:,:,n),ones(round(line_len/line_thickness_divisor)), 'valid'); 88 | Lthick(:,:,n) = Ln / max(max(Ln)); 89 | end 90 | 91 | % create the sketch 92 | G = zeros(size(J,1), size(J,2), 8); 93 | for n=1:8 94 | G(:,:,n) = conv2(Imag, L(:,:,n), 'same'); 95 | end 96 | 97 | [Gmax, Gindex] = max(G, [], 3); 98 | C = zeros(size(J,1), size(J,2), 8); 99 | for n=1:8 100 | C(:,:,n) = Imag .* (Gindex == n); 101 | end 102 | 103 | Spn = zeros(size(J,1), size(J,2), 8); 104 | for n=1:8 105 | Spn(:,:,n) = conv2(C(:,:,n), Lthick(:,:,n), 'same'); 106 | end 107 | Sp = sum(Spn, 3); 108 | Sp = (Sp - min(Sp(:))) / (max(Sp(:)) - min(Sp(:))); 109 | S = 1 - Sp; 110 | 111 | 112 | % ============================================== 113 | % Compute the texture tone drawing 'T' 114 | % ============================================== 115 | % new tone adjusted image 116 | Jadjusted = natural_histogram_matching(J,type); 117 | 118 | % stich pencil texture image 119 | texture = imread(texture_file_name); 120 | texture = texture(100:size(texture,1)-100,100:size(texture,2)-100); 121 | texture = im2double(imresize(texture, texture_resize_ratio*min([size(J,1),size(J,2)])/1024)); 122 | Jtexture = vertical_stitch(horizontal_stitch(texture,size(J,2)), size(J,1)); 123 | 124 | % solve for beta 125 | sizz = size(J,1)*size(J,2); % width of big matrix 126 | 127 | nzmax = 2*(sizz-1); 128 | i = zeros( nzmax, 1 ); 129 | j = zeros( nzmax, 1 ); 130 | s = zeros( nzmax, 1 ); 131 | for m=1:nzmax 132 | i(m) = ceil((m+0.1) / 2); 133 | j(m) = ceil((m-0.1) / 2); 134 | s(m) = -2*mod(m,2) + 1; 135 | end 136 | dx = sparse(i,j,s,sizz,sizz,nzmax); 137 | 138 | nzmax = 2*(sizz - size(J,2)); 139 | i = zeros( nzmax, 1 ); 140 | j = zeros( nzmax, 1 ); 141 | s = zeros( nzmax, 1 ); 142 | for m=1:nzmax 143 | if mod(m,2) 144 | i(m) = ceil((m+0.1) / 2); 145 | else 146 | i(m) = ceil((m-1+0.1) / 2) + size(J,2); 147 | end 148 | j(m) = ceil((m-0.1) / 2); 149 | s(m) = -2*mod(m,2) + 1; 150 | end 151 | dy = sparse(i,j,s,sizz,sizz,nzmax); 152 | 153 | Jtexture1d = log(reshape(Jtexture',1,[])); 154 | Jtsparse = spdiags(Jtexture1d',0,sizz,sizz); 155 | Jadjusted1d = log(reshape(Jadjusted',1,[])'); 156 | beta1d = (Jtsparse'*Jtsparse + lambda*(dx'*dx + dy'*dy))\(Jtsparse'*Jadjusted1d); 157 | beta = reshape(beta1d, size(J,2), size(J,1))'; 158 | 159 | % compute the texture tone image 'T' and combine it with the outline sketch 160 | % to come out with the final result 'Ipencil' 161 | T = Jtexture .^ beta; 162 | T = (T - min(T(:))) / (max(T(:)) - min(T(:))); 163 | Ipencil = S.*T; 164 | -------------------------------------------------------------------------------- /textures/a.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/fumin/pencil/31c5fd8cf4112e17592db5be1acf39aa8670e074/textures/a.jpg -------------------------------------------------------------------------------- /textures/d.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/fumin/pencil/31c5fd8cf4112e17592db5be1acf39aa8670e074/textures/d.jpg -------------------------------------------------------------------------------- /textures/texture.jpg: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/fumin/pencil/31c5fd8cf4112e17592db5be1acf39aa8670e074/textures/texture.jpg -------------------------------------------------------------------------------- /vertical_stitch.m: -------------------------------------------------------------------------------- 1 | function Istitched = vertical_stitch(I,height) 2 | % I must be within 0 and 1 3 | Istitched = I; 4 | while size(Istitched,1) 2 | ## 3 | ## This program is free software; you can redistribute it and/or modify it under 4 | ## the terms of the GNU General Public License as published by the Free Software 5 | ## Foundation; either version 3 of the License, or (at your option) any later 6 | ## version. 7 | ## 8 | ## This program is distributed in the hope that it will be useful, but WITHOUT 9 | ## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 10 | ## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more 11 | ## details. 12 | ## 13 | ## You should have received a copy of the GNU General Public License along with 14 | ## this program; if not, see . 15 | 16 | ## -*- texinfo -*- 17 | ## @deftypefn {Function File} {@var{cmap} =} ycbcr2rgb (@var{YCbCrmap}) 18 | ## @deftypefnx {Function File} {@var{RGB} =} ycbcr2rgb (@var{YCbCr}) 19 | ## @deftypefnx {Function File} {@dots{} =} ycbcr2rgb (@dots{}, [@var{Kb} @var{Kr}]) 20 | ## @deftypefnx {Function File} {@dots{} =} ycbcr2rgb (@dots{}, @var{standard}) 21 | ## Convert YCbCr color space to RGB. 22 | ## 23 | ## The convertion changes the image @var{YCbCr} or colormap @var{YCbCrmap}, 24 | ## from the YCbCr (luminance, chrominance blue, and chrominance red) 25 | ## color space to RGB values. @var{YCbCr} must be of class double, single, 26 | ## uint8, or uint16. 27 | ## 28 | ## The formula used for the conversion is dependent on two constants, @var{Kb} 29 | ## and @var{Kr} which can be specified individually, or according to existing 30 | ## standards: 31 | ## 32 | ## @table @asis 33 | ## @item "601" (default) 34 | ## According to the ITU-R BT.601 (formerly CCIR 601) standard. Its values 35 | ## of @var{Kb} and @var{Kr} are 0.114 and 0.299 respectively. 36 | ## @item "709" (default) 37 | ## According to the ITU-R BT.709 standard. Its values of @var{Kb} and 38 | ## @var{Kr} are 0.0722 and 0.2116 respectively. 39 | ## @end table 40 | ## 41 | ## @seealso{hsv2rgb, ntsc2rgb, rgb2hsv, rgb2ntsc, rgb2ycbcr} 42 | ## @end deftypefn 43 | 44 | function rgb = ycbcr2rgb (ycbcr, standard = "601") 45 | if (nargin < 1 || nargin > 2) 46 | print_usage (); 47 | endif 48 | rgb = ycbcrfunc ("ycbcr2rgb", ycbcr, standard); 49 | endfunction 50 | 51 | %!assert (ycbcr2rgb (rgb2ycbcr (jet (10))), jet (10), 0.00001); 52 | 53 | ## Copyright (C) 2013 CarnĂŤ Draug 54 | ## 55 | ## This program is free software; you can redistribute it and/or modify 56 | ## it under the terms of the GNU General Public License as published by 57 | ## the Free Software Foundation; either version 3 of the License, or 58 | ## (at your option) any later version. 59 | ## 60 | ## This program is distributed in the hope that it will be useful, 61 | ## but WITHOUT ANY WARRANTY; without even the implied warranty of 62 | ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 63 | ## GNU General Public License for more details. 64 | ## 65 | ## You should have received a copy of the GNU General Public License 66 | ## along with this program; if not, see . 67 | 68 | ## Private function for ycbcr2rgb and rgb2ycbcr functions which are 69 | ## very similar 70 | 71 | function out = ycbcrfunc (func, in, standard) 72 | 73 | img = false; # was input an image? 74 | if (iscolormap (in)) 75 | ## do nothing, it's a colormap 76 | elseif (isrgb (in)) 77 | img = true; 78 | ## we shape it as a colormap (2D matrix) so we can use matrix multiplcation 79 | nRows = rows (in); 80 | nCols = columns (in); 81 | in = reshape (in, [nRows*nCols 3]); 82 | else 83 | error ("%s: input must be a colormap (Nx3) or RGB image (NxMx3)", func); 84 | endif 85 | 86 | if (ischar (standard)) 87 | if (strcmpi (standard, "601")) # for ITU-R BT.601 88 | Kb = 0.114; 89 | Kr = 0.299; 90 | elseif (strcmpi (standard, "709")) # for ITU-R BT.709 91 | Kb = 0.0722; 92 | Kr = 0.2126; 93 | else 94 | error ("%s: unknown standard `%s'", func, standard); 95 | endif 96 | elseif (isnumeric (standard) && numel (standard) == 2) 97 | Kb = standard(1); 98 | Kr = standard(2); 99 | else 100 | error ("%s: must specify a standard (string), or Kb and Kr values", func); 101 | endif 102 | 103 | ## the color matrix for the conversion. Derived from: 104 | ## Y = Kr*R + (1-Kr-Kb)*G + kb*B 105 | ## Cb = (1/2) * ((B-Y)/(1-Kb)) 106 | ## Cr = (1/2) * ((R-Y)/(1-Kr)) 107 | ## It expects RGB values in the range [0 1], and returns Y in the 108 | ## range [0 1], and Cb and Cr in the range [-0.5 0.5] 109 | cmat = [ Kr (1-Kr-Kb) Kb 110 | -(Kr/(2-2*Kb)) -(1-Kr-Kb)/(2-2*Kb) 0.5 111 | 0.5 -(1-Kr-Kb)/(2-2*Kr) -(Kb/(2-2*Kr)) ]; 112 | 113 | cls = class (in); 114 | in = im2double (in); 115 | 116 | ## note that these blocks are the inverse of one another. Changes 117 | ## in one will most likely require a change on the other 118 | if (strcmp (func, "rgb2ycbcr")) 119 | ## convert to YCbCr colorspace 120 | out = (cmat * in')'; # transpose at the end to get back colormap shape 121 | ## rescale Cb and Cr to range [0 1] 122 | out(:, [2 3]) += 0.5; 123 | ## footroom and headroom will take from the range 16/255 each for Cb and Cr, 124 | ## and 16/255 and 20/255 for Y. So we have to compress the values of the 125 | ## space, and then shift forward 126 | out(:,1) = (out(:,1) * 219/255) + 16/255; 127 | out(:,[2 3]) = (out(:,[2 3]) * 223/255) + 16/255; 128 | 129 | elseif (strcmp (func, "ycbcr2rgb")) 130 | ## just the inverse of the rgb2ycbcr conversion 131 | in(:,[2 3]) = (in(:,[2 3]) - 16/255) / (223/255); 132 | in(:,1) = (in(:,1) - 16/255) / (219/255); 133 | in(:,[2 3]) -= 0.5; 134 | out = (inv (cmat) * in')'; 135 | else 136 | error ("internal error for YCbCr conversion. Unknown function %s", func); 137 | endif 138 | 139 | switch (cls) 140 | case {"single", "double"} 141 | ## do nothing. All is good 142 | case "uint8" 143 | out = im2uint8 (out); 144 | case "uint16" 145 | out = im2uint16 (out); 146 | otherwise 147 | error ("%s: unsupported image class %s", func, cls); 148 | endswitch 149 | 150 | if (img) 151 | ## put the image back together 152 | out = reshape (out, [nRows nCols 3]); 153 | endif 154 | 155 | endfunction 156 | --------------------------------------------------------------------------------