Что такое ppmreader и как открыть файл ppm в matlab

Question

Я пытаюсь открыть .ppm-файл в matlab Как мне это сделать?

i = imread('pic.ppm'); 

Есть читатели ppm онлайн. что такое преобразование этого файла? и как я читаю из файла ppm?

Answer 1

Синтаксис

A = imread(filename, fmt) 
[X, map] = imread(...) 
[...] = imread(filename) 
[...] = imread(URL,...) 
[...] = imread(...,Param1,Val1,Param2,Val2...) 

Answer 2

function [ r, g, b ] = ppma_read (file_name) 

%*****************************************************************************80 
% 
%% PPMA_READ opens an ASCII PPM file and reads the data. 
% 
% The PPMA file is assumed to have the format: 
% 
% P3 
% # feep.ppma 
% ncol nrow 
% maxrgb, the largest legal value for the data. 
% row 1, a list of ncol triples between 0 and maxrgb. 
% row 2, a list of ncol triples between 0 and maxrgb. 
% ... 
% row nrow, a list of ncol triples between 0 and maxrgb. 
% 
% Lines beginning with '#' are comments. 
% 
% Example: 
% 
% P3 
% # feep.ppma 
% 4 4 
% 15 
%  0 0 0 0 0 0 0 0 0 15 0 15 
%  0 0 0 0 15 7 0 0 0 0 0 0 
%  0 0 0 0 0 0 0 15 7 0 0 0 
% 15 0 15 0 0 0 0 0 0 0 0 0 
% 
% Licensing: 
% 
% This code is distributed under the GNU LGPL license. 
% 
% Modified: 
% 
% 21 February 2004 
% 
% Author: 
% 
% John Burkardt 
% 
% Parameters: 
% 
% Input, string FILE_NAME, the name of the PPMA file to read. 
% 
% Output, integer R{NROW,NCOL], G{NROW,NCOL], B{NROW,NCOL] is the RGB data read from the file. 
% 
    FALSE = 0; 
    TRUE = 1; 

    r = []; 
    g = []; 
    b = []; 

    fid = fopen (file_name, 'r'); 

    if (fid < 0) 
    fprintf (1, '\n'); 
    fprintf (1, 'PPMA_READ - Fatal error!\n'); 
    fprintf (1, ' Could not open the input file.\n'); 
    error ('PPMA_READ - Fatal error!'); 
    return; 
    end 
% 
% Read the first line. 
% 
    line = fgets (fid); 
% 
% Verify that the first two characters are the "magic number". 
% Matlab strncmp returns 1 for equality, and 0 for inequality. 
% 
    if (strncmp (line, 'P3', 2) == 0) 
    return; 
    end 
% 
% Move to the next noncomment line. 
% 
    while (1) 
    line = fgets (fid); 
    if (line(1) ~= '#') 
     break; 
    end 
    end 
% 
% Extract NCOL and NROW. 
% 
    [ array, count ] = sscanf (line, '%d'); 
    ncol = array(1); 
    nrow = array(2); 
% 
% Move to the next noncomment line. 
% 
    while (1) 
    line = fgets (fid); 
    if (line(1) ~= '#') 
     break; 
    end 
    end 
% 
% Extract MAXRGB, and ignore it. 
% 
    [ array, count ] = sscanf (line, '%d'); 
    maxRGB = array(1); 
% 
% Set aside space for R, G< B. 
% 
    r = zeros (nrow, ncol); 
    g = zeros (nrow, ncol); 
    b = zeros (nrow, ncol); 

    i = 1; 
    j = 0; 
    p = 0; 
    done = FALSE; 

    while (done == FALSE) 
% 
% Move to the next noncomment line. 
% 
    while (1) 
     line = fgets (fid); 
     if (line(1) ~= '#') 
     break; 
     end 
    end 
    [ array, count ] = sscanf (line, '%d'); 
% 
% Each value that you read goes into the "next" open entry. 
% When reading R, we update the row and column indices. 
% 
    for k = 1 : count 

     if (p == 0) 
     j = j + 1; 
     if (ncol < j) 
      j = 1; 
      i = i + 1; 
     end 
     r(i,j) = array(k); 
     elseif (p == 1) 
     g(i,j) = array(k); 
     elseif (p == 2) 
     b(i,j) = array(k); 
     if (i == nrow & j == ncol) 
      done = TRUE; 
     end 
     end 

     p = mod (p+1, 3); 

    end 

    end 

    fclose (fid); 

    return 
end