两种常见的图像放置在区域内的计算方法

get-img-contain-to-rect-config.js

function getImgContainToRectConfig (outerWidth, outerHeight, imgWidth, imgHeight) => {
	let newWidth = outerWidth;
	let newHeight = outerWidth * imgHeight / imgWidth;
	if (newHeight > outerHeight) {
	  newHeight = outerHeight;
	  newWidth = outerHeight * imgWidth / imgHeight;
	}
	return {
		top: (outerHeight - newHeight) / 2,
		left: (outerWidth - newWidth) / 2,
		width: newWidth,
		height: newHeight
	}
}

get-img-cover-to-rect-config.js

function getImgCoverToRectConfig(outerWidth, outerHeight, imgWidth, imgHeight) => {
	let newWidth = outerWidth;
	let newHeight = outerWidth * imgHeight / imgWidth;
	if (newHeight < outerHeight) {
	  newHeight = outerHeight;
	  newWidth = outerHeight * imgWidth / imgHeight;
	}
	return {
		top: (outerHeight - newHeight) / 2,
		left: (outerWidth - newWidth) / 2,
		width: newWidth,
		height: newHeight
	}
}