How can I encode images to Base64?

Hi, I want to encode an image to Base64, but the result is completely different than when I encode the image on this page.

I don't understand what I am doing wrong, is it me or the page I am using?

Here is my code (Google Bard helped me):

function encoded_string = base64encode_image(image)

image_uint8 = im2uint8(image);

encoded_bytes = zeros(1, length(image_uint8) * 4 / 3);

for i = 1:length(image_uint8)

encoded_bytes(4 * (i - 1) + 1:4 * i) = base64_chars(image_uint8(i) / 64 + 1);

encoded_bytes(4 * i + 1:4 * i + 2) = base64_chars((image_uint8(i) % 64) / 8 + 1);

encoded_bytes(4 * i + 2:4 * i + 3) = base64_chars((image_uint8(i) % 8) + 1);

end

encoded_string = char(encoded_bytes);

while length(encoded_string) % 3 ~= 0

encoded_string = [encoded_string "="];

end

end

Thank you!

[Les Beckham]

I don't see how you got any result at all from this code. It is not valid Matlab code.

The % character is the comment delimiter in Matlab (not the modulo operator like in C), so three of these lines will generate syntax errors.

[Dyuman Joshi]

In addition to Les's comment, the code assumes that length(image_uint8) will be divisible by 3, which is not guaranteed.

If you want to try an AI, try the AI Chat Playground by TMW

[Laszlo]

Sorry, but the code was generated by Google's Bard AI, I'll try the AI mentioned above and see if I can get ahead. Thank you.

This looks like simpler code, but I get this error: Unrecognised function or variable 'base64encode'.

% Read image file

img = imread('image.jpg');

% Convert image to base64 string

b64 = base64encode(img);

% Display base64 string

disp(b64);

[Dyuman Joshi]

The error is clear, MATLAB does not know what the parameter base64encode is. Thus, it does not know what to do with that command.

It's most likely a function, like the one you posted in your question i.e. base64encode_image.

From where did you get this particular snippet of code?

[Les Beckham]

There is at least one base64 image encoder on the File Exchange.

https://www.mathworks.com/matlabcentral/fileexchange/24514-base64-image-encoder?s_tid=ta_fx_results

[Laszlo]

Dyuman Joshi: I got the second code from here: https://in.mathworks.com/matlabcentral/playground/new

Les Beckham: Thanks a lot, I will try it: https://www.mathworks.com/matlabcentral/fileexchange/24514-base64-image-encoder?s_tid=ta_fx_results

Thanks to both of you, have a great day!

[Dyuman Joshi]

Hmmm. So, I asked the AI the same thing as well. I have attached pictures as to how it went.

which base64encode -all

'base64encode' not found.

And it was a bit weird. It references a function that does not exist and mentions the latest version as R2021a.

I tested for the function in my R2021a as well, but it had the same output i.e. not found.

But I did find this - matlab.net.base64encode, but that expects the inputs as either string, character vector or a numeric vector.

[DGM]

Aside from the AI being consistently misleading about how to access it and how to use it, that could be used. At least that would avoid a FEX dependency.

% encode only the raw image data
inpict = imread('peppers.png');

V = matlab.net.base64encode(inpict(:));
outpict = matlab.net.base64decode(V);
outpict = reshape(outpict,size(inpict));

imshow(outpict)

As to whether it matches some other encoder, I suppose that depends on what you're comparing. If you encode a JPG image, you're encoding the entire file as a byte stream -- the header, the metadata, the compressed raster data. If you read the image with imread(), you're just encoding an arbitrarily vectorized bunch of raw uncompressed image data. If you fed the latter to your web browser, it probably wouldn't know what to do with it.

% encode the file itself
fid = fopen('peppers.png');
V = fread(fid,'*uint8');
fclose(fid);
V = matlab.net.base64encode(V); % a web browser could read this

Answer 1

[Hassaan]

@Laszlo Try this out and matches the online tool.

To correctly encode a JPEG image to Base64 in MATLAB, the key is to read the image file as a raw byte stream, not as an image. This is because when MATLAB reads an image using imread, it converts the image into a matrix format suitable for image processing, which is not what you want for Base64 encoding.

1. Read the JPEG image file as raw bytes.
2. Encode these bytes into a Base64 string.

Image Input

% Specify the path to your JPEG image
imagePath = 'image.jpeg';

% Open the file in binary read mode
fileID = fopen(imagePath, 'rb');

% Read the file as bytes
imageBytes = fread(fileID, '*uint8');

% Close the file
fclose(fileID);

% Encode the byte array into Base64
encodedBase64 = matlab.net.base64encode(imageBytes);

% Display the Base64 encoded string using 'matlab.net.base64encode'
disp(encodedBase64);

% Encode the byte array into Base64 using custom function 'base64encode'
encodedBase64Custom = base64encode(imageBytes);

% Display the Base64 encoded string using my custom function
disp(encodedBase64);

% This function takes an array of uint8 data, converts it to a binary string,
% chunks this string into 6-bit segments, maps these to Base64 characters, 
% and adds necessary padding.
function encodedString = base64encode(inputData)
    % Define the Base64 characters
    base64Chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
    
    % Convert input data to uint8 if it's not already
    if ~isa(inputData, 'uint8')
        error('Input must be a uint8 array.');
    end

    % Convert the data to binary string
    binaryString = reshape(dec2bin(inputData, 8)', 1, []);

    % Pad the binary string so its length is a multiple of 6
    paddedBinaryString = [binaryString, repmat('0', 1, mod(-length(binaryString), 6))];

    % Initialize the encoded string
    encodedString = '';

    % Map each 6-bit chunk to a Base64 character
    for i = 1:6:length(paddedBinaryString)
        sixBitChunk = paddedBinaryString(i:i+5);
        decimalValue = bin2dec(sixBitChunk);
        encodedString = [encodedString, base64Chars(decimalValue+1)];
    end

    % Add padding characters
    paddingLength = mod(-length(inputData), 3);
    if paddingLength > 0
        encodedString(end+1:end+paddingLength) = '=';
    end
end

MATLAB code with my image:

/9j/4AAQSkZJRgABAQEA8ADwAAD/2wBDAAMCAgMCAgMDAwMEAwMEBQgFBQQEBQoHBwYIDAoMDAsKCwsNDhIQDQ ...

Online tool [Online Base64 Encoder: Encode Text or File to Base64 - B64Encode] with my image:

/9j/4AAQSkZJRgABAQEA8ADwAAD/2wBDAAMCAgMCAgMDAwMEAwMEBQgFBQQEBQoHBwYIDAoMDAsKCwsNDhIQDQ ...

Will read the JPEG image as a binary file, preserving its original byte format, and then encode these bytes into a Base64 string.

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[Dyuman Joshi]

Which image and online tool did you use?

You should mention such details in the answer itself.

[Hassaan]

@Dyuman Joshi The same tool the OP mentioned:

Online Base64 Encoder: Encode Text or File to Base64 - B64Encode

I have updated.