背景:做petct过程中,前端的PT图像可以正常显示窗框窗位,后端要做截图时不能正确显示窗宽窗位。
解决思路:前端可以正常显示是因为 cornerstone.js 的源码里有算法做过处理,可以参考源码算法。
computeAutoVoi.js 中的源码贴出来记录一下:
javascript
/**
* Computes the VOI to display all the pixels if no VOI LUT data (Window Width/Window Center or voiLUT) exists on the viewport object.
*
* @param {Viewport} viewport - Object containing the viewport properties
* @param {Object} image An Image loaded by a Cornerstone Image Loader
* @returns {void}
* @memberof Internal
*/
export default function computeAutoVoi (viewport, image) {
if (hasVoi(viewport)) {
return;
}
const maxVoi = image.maxPixelValue * image.slope + image.intercept;
const minVoi = image.minPixelValue * image.slope + image.intercept;
const ww = maxVoi - minVoi;
const wc = (maxVoi + minVoi) / 2;
if (viewport.voi === undefined) {
viewport.voi = {
windowWidth: ww,
windowCenter: wc
};
} else {
viewport.voi.windowWidth = ww;
viewport.voi.windowCenter = wc;
}
}
核心代码就是:
javascript
// 从图像的dicom标签中可以拿到图像最大像素值/最小像素值*图像斜率+图像的截距
const maxVoi = image.maxPixelValue * image.slope + image.intercept;
const minVoi = image.minPixelValue * image.slope + image.intercept;
// 窗宽
const ww = maxVoi - minVoi;
// 窗位
const wc = (maxVoi + minVoi) / 2;