NativeScript/nativescript-core/image-source/image-source-common.ts

export function getScaledDimensions(
    width: number,
    height: number,
    maxSize: number
) {
    if (height >= width) {
        if (height <= maxSize) {
            // if image already smaller than the required height
            return { width, height };
        }

        return {
            width: Math.round((maxSize * width) / height),
            height: maxSize
        };
    }

    if (width <= maxSize) {
        // if image already smaller than the required width
        return { width, height };
    }

    return {
        width: maxSize,
        height: Math.round((maxSize * height) / width)
    };
}