tensorflow-helpers/image-utils.js

Helper functions to use tensorflow in nodejs for transfer learning, image classification, and more

"use strict";
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Object.defineProperty(exports, "__esModule", { value: true });
exports.getImageTensorShape = getImageTensorShape;
exports.calcCropBox = calcCropBox;
exports.cropAndResizeImageTensor = cropAndResizeImageTensor;
const tf = __importStar(require("@tensorflow/tfjs-core"));
const tensor_1 = require("./tensor");
function getImageTensorShape(imageTensor) {
    return imageTensor.shape.length === 3
        ? {
            width: imageTensor.shape[1],
            height: imageTensor.shape[0],
        }
        : {
            width: imageTensor.shape[2],
            height: imageTensor.shape[1],
        };
}
/**
 * @description calculate center-crop box
 * @returns [top,left,bottom,right], values range: 0..1
 */
function calcCropBox(options) {
    let { sourceShape, targetShape } = options;
    let top = 0;
    let left = 0;
    let bottom = 1;
    let right = 1;
    if (sourceShape.width > sourceShape.height ==
        targetShape.width > targetShape.height) {
        let targetHeightInRatio = (sourceShape.height / sourceShape.width) * targetShape.width;
        top =
            Math.abs(targetHeightInRatio - targetShape.height) /
                targetHeightInRatio /
                2;
        bottom = 1 - top;
    }
    else {
        let targetWidthInRatio = (sourceShape.width / sourceShape.height) * targetShape.height;
        left =
            Math.abs(targetWidthInRatio - targetShape.width) / targetWidthInRatio / 2;
        right = 1 - left;
    }
    return [top, left, bottom, right];
}
function cropAndResizeImageTensor(options) {
    let { imageTensor, width, height } = options;
    let croppedImageTensor = tf.tidy(() => {
        let imageShape = getImageTensorShape(imageTensor);
        let cropBox = options.aspectRatio != 'center-crop'
            ? [0, 0, 1, 1]
            : calcCropBox({
                sourceShape: imageShape,
                targetShape: { width, height },
            });
        const crop = tf.image.cropAndResize(
        // Expand image input dimensions to add a batch dimension of size 1.
        (0, tensor_1.toTensor4D)(imageTensor), [cropBox], [0], [height, width]);
        return crop.div(255);
    });
    imageTensor.dispose();
    return croppedImageTensor;
}