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Fast way to add elements into an Uint8ClampedArray typed array


Fast way to add elements into an Uint8ClampedArray typed array

By : Nirat
Date : October 21 2020, 08:10 AM
I wish this helpful for you Consider the following:
Construct a Uint8ClampedArray TypedArray instead of the standard Array ─ this would lower memory consumption and speed up writes Remove line duplicates and the unnecessary else block Prepopulate max iterations Use strict comparison
code :
function addIndexes(indexesToAdd, typedArray) {
  var newArray = new Uint8ClampedArray(indexesToAdd.length + typedArray.length);
  var index = 0;
  var max = typedArray.length;
  var c = 0;
  for(var i=0;i<max;i++) {
    newArray[c] = typedArray[i];
    if (i !== indexesToAdd[index]) {
      c++;
      newArray[c] = 0;
    }
    c++;
    index++;
  }
  return newArray;
}


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Convert Uint8ClampedArray to regular array

Convert Uint8ClampedArray to regular array


By : user3536397
Date : March 29 2020, 07:55 AM
will be helpful for those in need You can convert a typed array to a regular array by using Array.prototype.slice
code :
var typedArray = new Uint8ClampedArray([1, 2, 3, 4]);
var normalArray = Array.prototype.slice.call(typedArray);
var normalArray = Array.from(typedArray);
How to convert a javascript array to Uint8ClampedArray which works in IE

How to convert a javascript array to Uint8ClampedArray which works in IE


By : Alpha Bravo
Date : March 29 2020, 07:55 AM
To fix this issue If you really have the array of every rgba value of each pixels, and the height/width of your image, then you can use this method :
To get a correct dataImage, in a cross-browser way, the only method is to call context.createImageData() method.
code :
var ctx = c.getContext('2d');

var drawArray = function(arr, width, height) {
  // set your canvas width/height
  c.width = width;
  c.height = height;
  
  // create the imageData object, you'll need the width and height of your image
  var dataImage = ctx.createImageData(width, height);
  // browsers supporting TypedArrays
  if (dataImage.data.set) {
    dataImage.data.set(arr);
  } else {
    // IE9
    arr.forEach(function(val, i) {
      dataImage.data[i] = val;
    });
  }
  ctx.putImageData(dataImage, 0, 0);
};

var pixelsArray = [0, 0, 0, 0, 170, 170, 170, 3, 0, 0, 0, 0, 0, 0, 0, 1, 170, 170, 170, 3, 0, 0, 0, 0, 170, 170, 170, 3, 127, 127, 127, 2, 0, 0, 0, 0, 127, 127, 127, 2, 170, 170, 170, 3, 0, 0, 0, 0, 170, 170, 170, 3, 0, 0, 0, 1, 0, 0, 0, 1, 170, 170, 170, 3, 170, 170, 170, 3, 0, 0, 0, 0, 154, 5, 119, 94, 255, 0, 192, 213, 244, 0, 182, 223, 225, 0, 171, 164, 93, 13, 80, 19, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 60, 15, 45, 17, 221, 0, 166, 159, 250, 0, 186, 224, 244, 0, 184, 210, 194, 0, 145, 84, 0, 0, 0, 0, 0, 0, 0, 0, 121, 18, 91, 84, 255, 0, 184, 255, 253, 0, 182, 252, 252, 0, 178, 254, 255, 0, 190, 255, 207, 0, 148, 204, 21, 0, 0, 12, 0, 0, 0, 4, 0, 0, 0, 8, 199, 0, 141, 196, 255, 0, 191, 255, 251, 0, 178, 252, 255, 0, 183, 254, 254, 0, 181, 255, 112, 18, 90, 68, 0, 0, 0, 0, 229, 0, 177, 192, 255, 0, 186, 255, 249, 0, 180, 242, 255, 0, 187, 255, 245, 0, 175, 240, 255, 0, 200, 255, 170, 0, 129, 156, 0, 0, 0, 0, 170, 0, 130, 150, 255, 0, 199, 255, 246, 0, 176, 240, 255, 0, 187, 255, 249, 0, 179, 241, 255, 0, 187, 255, 224, 0, 173, 178, 127, 127, 127, 2, 240, 0, 181, 214, 255, 0, 182, 255, 253, 0, 182, 251, 255, 0, 183, 255, 253, 0, 182, 254, 250, 0, 183, 254, 237, 0, 181, 241, 113, 0, 87, 99, 240, 0, 184, 241, 249, 0, 182, 254, 255, 0, 182, 253, 255, 0, 183, 255, 252, 0, 182, 250, 255, 0, 183, 255, 235, 0, 178, 208, 0, 0, 0, 0, 238, 0, 180, 203, 255, 0, 184, 255, 252, 0, 182, 249, 255, 0, 183, 255, 251, 0, 184, 253, 251, 0, 190, 255, 246, 0, 192, 252, 244, 0, 198, 249, 245, 0, 191, 252, 252, 0, 190, 255, 251, 0, 184, 253, 255, 0, 183, 255, 252, 0, 181, 248, 255, 0, 185, 255, 237, 0, 179, 200, 0, 0, 0, 0, 192, 3, 148, 143, 255, 0, 188, 255, 249, 0, 180, 246, 254, 0, 186, 255, 248, 0, 187, 253, 246, 0, 192, 255, 241, 0, 196, 254, 235, 0, 197, 251, 242, 0, 197, 254, 246, 0, 192, 255, 248, 0, 187, 253, 254, 0, 186, 255, 250, 0, 181, 246, 255, 0, 185, 255, 200, 1, 154, 145, 0, 0, 0, 0, 111, 19, 85, 39, 239, 0, 176, 245, 252, 0, 186, 250, 250, 0, 188, 254, 247, 0, 193, 255, 241, 0, 195, 254, 238, 0, 202, 255, 235, 0, 205, 254, 237, 0, 201, 255, 242, 0, 196, 255, 247, 0, 193, 255, 249, 0, 188, 254, 249, 0, 183, 249, 246, 0, 182, 249, 104, 17, 81, 44, 212, 212, 212, 6, 0, 0, 0, 0, 128, 0, 90, 101, 255, 0, 204, 255, 233, 0, 182, 246, 246, 0, 200, 255, 236, 0, 200, 254, 233, 0, 206, 255, 228, 0, 209, 254, 233, 0, 206, 255, 236, 0, 200, 254, 245, 0, 199, 255, 236, 0, 184, 245, 255, 0, 206, 255, 116, 0, 84, 109, 0, 0, 0, 0, 0, 0, 0, 0, 36, 0, 36, 7, 0, 0, 0, 0, 134, 0, 106, 110, 255, 0, 216, 255, 230, 0, 195, 247, 237, 0, 208, 255, 227, 0, 209, 254, 226, 0, 215, 255, 227, 0, 209, 254, 235, 0, 208, 255, 234, 0, 199, 247, 253, 0, 206, 255, 134, 0, 105, 116, 0, 0, 0, 0, 36, 0, 36, 7, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 9, 0, 0, 0, 0, 133, 0, 112, 111, 242, 0, 213, 255, 224, 0, 206, 247, 227, 0, 218, 255, 218, 0, 217, 253, 227, 0, 219, 255, 220, 0, 204, 247, 247, 0, 218, 255, 111, 0, 93, 114, 0, 0, 0, 0, 28, 0, 0, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 10, 0, 0, 0, 0, 156, 0, 143, 135, 239, 0, 229, 255, 213, 0, 214, 245, 222, 0, 231, 255, 214, 0, 215, 246, 239, 0, 230, 255, 165, 0, 152, 137, 0, 0, 0, 0, 25, 0, 25, 10, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 172, 0, 173, 173, 226, 0, 237, 255, 201, 0, 219, 242, 224, 0, 235, 255, 174, 0, 176, 184, 0, 0, 0, 0, 0, 0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 2, 30, 0, 30, 17, 203, 0, 220, 216, 214, 0, 239, 255, 215, 0, 234, 233, 61, 0, 69, 33, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 65, 0, 78, 62, 219, 0, 251, 255, 86, 0, 100, 91, 0, 0, 0, 0, 31, 0, 31, 8, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 51, 51, 102, 5, 142, 50, 157, 86, 56, 56, 56, 9, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0];

drawArray(pixelsArray, 16, 16);
<canvas id="c"></canvas>
Sending uint8clampedarray Array via ajax to c# in javaScript after getImageData from Canvas

Sending uint8clampedarray Array via ajax to c# in javaScript after getImageData from Canvas


By : fushimik
Date : March 29 2020, 07:55 AM
should help you out The solution I found was to generate the canvas image data differently (old way).
Generate Image Differently
code :
function getSignatureImage() {
    //return ctx.getImageData(0, 0, canvas.width, canvas.height).data;
    var pic = canvas.toDataURL("image/png");
    pic = pic.replace(/^data:image\/(png|jpg);base64,/, "")
    return pic;
} 
$.ajax({
    type: "POST",
    data: '{"imageData" : "'+ signatureImage + '" }',
    ....
public static string SetSignature(string imageData)
{
    string filePath = HttpContext.Current.Server.MapPath("Signature.png");
    using (FileStream fs = new FileStream(filePath, FileMode.Create))
    {
        using (BinaryWriter bw = new BinaryWriter(fs))
        {
            byte[] data = Convert.FromBase64String(imageData);
            bw.Write(data);
            bw.Close();
        }
    }
}
Fast way of relabeling array elements or making elements contiguous in python

Fast way of relabeling array elements or making elements contiguous in python


By : user3527691
Date : March 29 2020, 07:55 AM
this one helps. I have a massive size 3d array to deal with. I want to relabel elements in following way , If the given array is unsorted, this will be quicker than sorting it:
code :
from numba import njit
import numpy as np

@njit()
def relabel_fast(array, count):
    i = 0
    while i < len(array):
        data = array[i]
        count[data] += 1
        i += 1
    a = 1 # Position in count
    b = 0 # Position in array
    c = 0 # The current output number
    while a < len(count):
        d = 0 # The number of 'c' to output
        if count[a] > 0:
            while d < count[a]:
                array[b] = c
                b += 1
                d += 1
            c += 1
        a += 1

def relabel(given_array):
    # Arrays cannot be created within Numba, so create the count array before calling the Numba function
    count = np.zeros(np.max(given_array) + 1, dtype=int)
    relabel_fast(given_array, count)


#given_array = np.array([1, 1, 1, 3, 3, 5, 5, 5, 8, 8, 8, 8, 8, 23, 23, 23])
given_array = np.array([1, 23, 1, 3, 8, 3, 5, 5, 8, 8, 8, 5, 8, 23, 23, 1])
relabel(given_array)

given_array
array([0, 0, 0, 1, 1, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4])
Fast python algorithm (in numpy or pandas?) to find indices of array elements that match elements in another array

Fast python algorithm (in numpy or pandas?) to find indices of array elements that match elements in another array


By : zvako
Date : March 29 2020, 07:55 AM
I wish did fix the issue. This can be done with pandas using map to map the data from one column using the data of another. Here's an example with sample data:
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