Get Height And Width Dimensions From Base64 Png

November 19, 2023 Post a Comment

I have this data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAOcAAABnCAYAAAD7RFX4AAAACXBIWXMAAAsTAAALEwEAmpwYAAAKT2lDQ1BQaG90b3Nob3AgSUNDIHByb2ZpbGUAAHjanVNnVFPpFj333vRCS4iAlEtvUhUIIF

Solution 1:

I’m sure that it’s possible to parse that out of the PNG somehow, but assuming data URI support (since we can assume atob), you can just create an image and wait for it to load (this works in any format):

var image = document.createElement('img');

image.addEventListener('load', function() {
    // image.width × image.height
});

image.src = 'data:image/png;base64,…';

Here's a demo.

Okay, apparently you’d like to extract this information manually. A PNG file starts with the bytes 89 50 4E 47 0D 01 1A 0A, followed by the IHDR chunk that contains the width and height and must be the first chunk. (Yay, easier!) A chunk has a 4-byte length, a 4-byte type, and then a length-byte content. IHDR’s content starts with a 4-byte width and a 4-byte height, so a PNG’s width and height are always bytes 16–24! This can all be checked if you like, but for a simple way that assumes the PNG is valid:

functiontoInt32(bytes) {
    return (bytes[0] << 24) | (bytes[1] << 16) | (bytes[2] << 8) | bytes[3];
}

functiongetDimensions(data) {
    return {
        width: toInt32(data.slice(16, 20)),
        height: toInt32(data.slice(20, 24))
    };
}

var base64Characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

functionbase64Decode(data) {
    var result = [];
    var current = 0;

    for(var i = 0, c; c = data.charAt(i); i++) {
        if(c === '=') {
            if(i !== data.length - 1 && (i !== data.length - 2 || data.charAt(i + 1) !== '=')) {
                thrownewSyntaxError('Unexpected padding character.');
            }

            break;
        }

        var index = base64Characters.indexOf(c);

        if(index === -1) {
            thrownewSyntaxError('Invalid Base64 character.');
        }

        current = (current << 6) | index;

        if(i % 4 === 3) {
            result.push(current >> 16, (current & 0xff00) >> 8, current & 0xff);
            current = 0;
        }
    }

    if(i % 4 === 1) {
        thrownewSyntaxError('Invalid length for a Base64 string.');
    }

    if(i % 4 === 2) {
        result.push(current >> 4);
    } elseif(i % 4 === 3) {
        current <<= 6;
        result.push(current >> 16, (current & 0xff00) >> 8);
    }

    return result;
}

functiongetPngDimensions(dataUri) {
    if (dataUri.substring(0, 22) !== 'data:image/png;base64,') {
        thrownewError('Unsupported data URI format');
    }

    // 32 base64 characters encode the necessary 24 bytesreturngetDimensions(base64Decode(dataUri.substr(22, 32)));
}

var dimensions = getPngDimensions('data:image/png;base64,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');

console.log(dimensions.width + ' × ' + dimensions.height);

Solution 2:

And here is a new updated es6 version 3 years later with a tiny bit of help from typed arrays that is synchronous and where you don't have to load the hole image to memory to figure it out. So its faster :)

also don't require any DOM so it can work inside Workers

functiongetPngDimensions(base64) {
  const header = atob(base64.slice(0, 50)).slice(16,24)
  const uint8 = Uint8Array.from(header, c => c.charCodeAt(0))
  const dataView = newDataView(uint8.buffer)

  return {
    width: dataView.getInt32(0),
    height: dataView.getInt32(4)
  }
}

// Just to get some base64 png exampleconst canvas = document.createElement('canvas')
const base64 = canvas.toDataURL().split(',')[1]

const dimensions = getPngDimensions(base64)
console.log(dimensions)

edit: my recommendation is also that you should try to use typed arrays instead of base64 and blobs instead of typed arrays when possible, base64 is the worse container and use more memory.

Baca Juga

So here is a solution for you who already have a blob:

document.createElement('canvas').toBlob(async blob => {
  // blob.arrayBuffer() is the new way to read stuff// may not work in all browserlet dv = newDataView(await blob.slice(16, 24).arrayBuffer())
  
  console.log({
    width: dv.getInt32(0),
    height: dv.getInt32(4)
  })
})

// you could also try out the new experimental createImageBitmap// don't use image or canvas but this also works in web workers// and it also works for more than just png's// could expect this is more havier/slower than just reading bytes 16-24document.createElement('canvas').toBlob(async blob => {
  const bitmap = awaitcreateImageBitmap(blob)
  const { width, height } = bitmap
  bitmap.close() // GCconsole.log({ width, height })
})

Solution 3:

LIVE DEMO

var imgData = 'data:image/png;base64,iVBORw0.........';    
var img = newImage();       
img.onload = function(){
  alert(img.width +' '+ img.height );
};
img.src = imgData;

Solution 4:

With jQuery:

var width, height;
$('<img/>').load(function(){
    width = $(this).width();
    height = $(this).height();
    // Call whatever function here that requires the width/height
}).attr('src', datauri)

Solution 5:

** in node.js

function getPNGSize (buffer) {
  if (buffer.toString('ascii', 12, 16) === 'CgBI') {
    return {
      'width': buffer.readUInt32BE(32),
      'height': buffer.readUInt32BE(36)
    };
  }
  return {
    'width': buffer.readUInt32BE(16),
    'height': buffer.readUInt32BE(20)
  };
}
getPNGSize(buffer)

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