Using a 'for' loop to read gif RGB and pixel index, cant get textscan with 'if' statement to work

Hello All,

I have been working on a porting program to take a gif frame by frame, read each pixel and RGB value, then put it into a formatted text file. I have gotten it to work but I am trying to make the code output smaller. I am trying to read each frame, then read the previous frame to see if the pixel index number and RGB value match, if they do not match, add a new entry into the formatted file. If there is a match just skip adding a entry and check the next pixel index number and RGB value. Here is my code,

sourceimage = '/Users/tapotter/Animations/leda36.gif'; %Pull file to load
numframes = numel(imfinfo(sourceimage)); %Pull the number of frames
fida = fopen('FastLEDAnimation.txt', 'a+'); %Open files to use.
fidp = fopen('previousframe.txt', 'wt+');   %Create and open a temporary file to check values against.
for frame = 1:numframes %Go through each frame of the gif
  [img, map] = imread(sourceimage, frame); % Open the image and create the map
  rgbimg = im2uint8(ind2rgb(img, map)); %turn the index into  unit8 rgb format
  crgb = reshape(permute(rgbimg, [3, 1, 2]), 3, []);  %makes a 3xnumpixels array
  framedelay = imfinfo(sourceimage); %Pulls the frame delay from imfinfo
  fdelay = framedelay.DelayTime; %Get the frame delay
  pixcrgb = [1:size(crgb, 2); double(crgb)];  %Sets up the readout to include what pixel its on but only goes through 255, then repeats 200 times with 255
  P = textscan(fidp, 'leds[%d].setRGB(%d, %d, %d);\n', pixcrgb'); %Go through and see if textscan can find these values
  if isempty(P) %If the textscan returns empty write to the file
    fprintf(fida, 'leds[%d].setRGB(%d, %d, %d);\n', pixcrgb);
  end
  fprintf(fida, '\nFastLED.delay(%d);\nFastLED.show();\n', fdelay); %Add the delay to the formatted text
  fprintf(fidp, 'leds[%d].setRGB(%d, %d, %d);\n', pixcrgb); %Add all of the current pixel 'index' numbers and RGB values for reference as the 'previous' frame next iteration
end
fclose(fida); %Close the files and delete the fidp file. 
fclose(fidp);
delete(fidp);
fprintf('\nComplete!\n\n');

Currently it does not return anything during the loop and never writes the 'fprintf(fida, 'leds[%d].setRGB(%d, %d, %d);\n', pixcrgb);' portion to the file. When looking at the previousframe.txt, it continously writes information and append's it. What I was hoping for was it would clear the previousframe.txt and only store the last frames values. I have tried a couple different loops but cant seem to wrap my head around it. Any suggestions on how I might right the loop section? Specifically this part is where I need help,

   P = textscan(fidp, 'leds[%d].setRGB(%d, %d, %d);\n', pixcrgb'); %Go through and see if textscan can find these values
    if isempty(P) %If the textscan returns empty write to the file
      fprintf(fida, 'leds[%d].setRGB(%d, %d, %d);\n', pixcrgb);
    end
    fprintf(fida, '\nFastLED.delay(%d);\nFastLED.show();\n', fdelay); %Add the delay to the formatted text
    fprintf(fidp, 'leds[%d].setRGB(%d, %d, %d);\n', pixcrgb); %Add all of the current pixel 'index' numbers and RGB values for reference as the 'previous' frame next iteration
  end

[Jan]

I'm surprised that this command does not throw an error:

P = textscan(fidp, 'leds[%d].setRGB(%d, %d, %d);\n', pixcrgb')

The 3rd argument is not valid, because textscan expects "N — Number of times to apply formatSpec", but not a matrix.

Answer 1

[Jan]

It is not clear, what you want to achieve. Do you want to omit writing e.g. "leds[1].setRGB(2, 3, 4)", if this string occurs in the former block already? Then using a file to store the temporary values is very indirect. Why not using the available values instead?

% [Code EDITED]
sourceimage = '/Users/tapotter/Animations/leda36.gif'; %Pull file to load
numframes   = numel(imfinfo(sourceimage)); %Pull the number of frames
fid         = fopen('FastLEDAnimation.txt', 'a+'); %Open files to use.
framedelay  = imfinfo(sourceimage);  % Once only outside the loop
fdelay      = framedelay.DelayTime;  % Get the frame delay
oldFrame    = Inf;                   % Arbitrary unique value
for iframe = 1:numframes %Go through each frame of the gif
  [img, map] = imread(sourceimage, iframe);
  rgbimg     = im2uint8(ind2rgb(img, map));
  crgb       = reshape(permute(rgbimg, [3, 1, 2]), 3, []);
  Frame      = [1:size(crgb, 2); double(crgb)];
  changed    = any(Frame ~= oldFrame, 1);
  oldFrame   = Frame;
  fprintf(fid, 'leds[%d].setRGB(%d, %d, %d);\n', Frame(:, changed));
  fprintf(fid, '\nFastLED.delay(%d);\nFastLED.show();\n', fdelay);
end
fclose(fid);
%  delete(fidp); % No DELETE for file identifier of closed file!
fprintf('\nComplete!\n\n');

Please read doc delete. If the former file identifier was e.g. 4. Then delete(4) tries to delete a figure with the handle 4. delete needs a file name for removing a file.

[Travis Potter]

If the value is found to match from the previous frame, example output

leds[23].setRGB(25, 167, 209);

I would need to compare the previous frame's pixel index and rgb value, if it finds,

leds[23].setRGB(25, 167, 209);

in the previous frame, omit adding the line in the animation file. This code returns this error

Error using ismember>ismemberR2012a (line 212)
Inputs A and B must be matrices with the same number of columns in the 'rows' case.

Error in ismember (line 146)
            lia = ismemberR2012a(A,B,logical(flaginds(1)));

[Jan]

I've edited the code: ismember('rows') replaced by the faster any(Frame == oldFrame).

[Travis Potter]

One last question, the pixel index starts at '1' in the file, but I need it to start at 0 and go to 483. How would I bring the

fprintf(fid, 'leds[%d].setRGB(%d, %d, %d);\n', Frame(:, changed));

To always minus 1 from the first variable '%d' in the "leds[]" section listed above.