NativeScript/tns-core-modules/image-asset/image-asset-common.ts

import { ImageAsset as ImageAssetDefinition, ImageAssetOptions } from ".";
import { Observable } from "../data/observable";
import { screen as platformScreen } from "../platform";

export class ImageAssetBase extends Observable implements ImageAssetDefinition {
    private _options: ImageAssetOptions;
    private _nativeImage: any;

    ios: PHAsset;
    android: string;

    constructor() {
        super();
        this._options = { keepAspectRatio: true, autoScaleFactor: true };
    }

    get options(): ImageAssetOptions {
        return this._options;
    }

    set options(value: ImageAssetOptions) {
        this._options = value;
    }

    get nativeImage(): any {
        return this._nativeImage;
    }

    set nativeImage(value: any) {
        this._nativeImage = value;
    }

    public getImageAsync(callback: (image: any, error: Error) => void) {
        //
    }
}

export function getAspectSafeDimensions(sourceWidth, sourceHeight, reqWidth, reqHeight) {
    let widthCoef = sourceWidth / reqWidth;
    let heightCoef = sourceHeight / reqHeight;
    let aspectCoef = Math.min(widthCoef, heightCoef);

    return {
        width: Math.floor(sourceWidth / aspectCoef),
        height: Math.floor(sourceHeight / aspectCoef)
    };
}

export function getRequestedImageSize(src: { width: number, height: number }, options: ImageAssetOptions): { width: number, height: number } {
    const screen = platformScreen.mainScreen;

    let reqWidth = options.width || Math.min(src.width, screen.widthPixels);
    let reqHeight = options.height || Math.min(src.height, screen.heightPixels);

    if (options && options.keepAspectRatio) {
        let safeAspectSize = getAspectSafeDimensions(src.width, src.height, reqWidth, reqHeight);
        reqWidth = safeAspectSize.width;
        reqHeight = safeAspectSize.height;
    }

    return {
        width: reqWidth,
        height: reqHeight
    };
}