JavaScript image similarity algorithm realizes _javascript technique of histogram and vector algorithm in JS

Copy Code code as follows:

function Gethistogram (imagedata) {
var arr = [];
for (var i = 0; i < i++) {
Arr[i] = 0;
}
var data = Imagedata.data;
var pow4 = Math.pow (4, 2);
for (var i = 0, len = data.length i < len; i = 4) {
var red = (Data[i]/64) | 0;
var green = (data[i + 1]/64) | 0;
var blue = (Data[i + 2]/64) | 0;
var index = red * pow4 + green * 4 + blue;
arr[index]++;
}

return arr;
}

Function cosine (arr1, arr2) {
    var axb = 0,
        a = 0,
        b = 0;
    for (var i = 0, len = arr1.length i < len; i++) {
        AXB + + arr1[i] * Arr2[i];
        a = arr1[i] * Arr1[i];
        B + + arr2[i] * Arr2[i];
   }
    return AXB/(MATH.SQRT (a) * MATH.SQRT (b));
}
Function Gray (imgdata) {
    var data = Imgdata.data
    for (var i = 0, len = data.length i < len; i = 4) {
        var Gray = parseint ((Data[i] + data[i + 1] + Data[i + 2])/3);
        data[i + 2] = data[i + 1] = data[i] = Gray;
   }
    return imgdata;
}

There is a problem, if the picture is gray to compare with the original, then to compare the similarity, you need to turn the picture into Gray, that is, using the above code gray function to deal with