微信小程序学习点滴《十二》：图片等比例缩放 获取屏幕尺寸图片尺寸 自适应

Posted 2020-09-07

原文：http://www.wxapp-union.com/portal.php?mod=view&aid=360

早上在论坛上看到有人写了关于图片等比例缩放的文章,只是判断了图片宽是否大于屏幕宽.我之前在做android的时候也会遇到图片等比例缩放的问题.应该是用图片宽高比和屏幕宽高比做判断.做个笔记.

老规矩,先上图.

1.图片高宽比小于屏幕高宽比

 

2.图片高宽比大于屏幕高宽比

 

3.这种其实也是图片高宽比小于屏幕高宽比,但是高宽都大于屏幕高宽.所以不能简单用高宽来判断,应该是用高宽比判断后做缩放.

 

上代码:

1.index.wxml

1. <!--index.wxml-->
2. <!--图片宽大于屏幕宽-->
3. <image style="width: {{imagewidth}}px; height: {{imageheight}}px;" src="{{imagefirstsrc}}" bindload="imageLoad"></image>
4. <!--图片高大于屏幕高-->
5. <!--<image style="width: {{imagewidth}}px; height: {{imageheight}}px;" src="{{imagesecondsrc}}" bindload="imageLoad"></image>-->
6. <!--图片宽高大于屏幕宽高-->
7. <!--<image style="width: {{imagewidth}}px; height: {{imageheight}}px;" src="{{imagethirdsrc}}" bindload="imageLoad"></image>-->

2.index.js

1. //index.js
2. //获取应用实例
3. var imageUtil = require(‘../../utils/util.js‘);
4. var app = getApp()
5. Page({
6. data: {
7. imagefirstsrc: ‘http://bpic.588ku.com/back_pic/00/03/85/1656205138bbe2d.png‘,//图片链接
8. imagesecondsrc: ‘http://bpic.588ku.com/back_pic/04/07/63/28581203949ca9d.jpg!/fw/400/quality/90/unsharp/true/compress/true‘,//图片链接
9. imagethirdsrc:‘http://img1.gtimg.com/ent/pics/hv1/13/71/2061/134034643.jpg‘,
10. imagewidth: 0,//缩放后的宽
11. imageheight: 0,//缩放后的高
13. },
14. onLoad: function () {
15. },
16. imageLoad: function (e) {
17. var imageSize = imageUtil.imageUtil(e)
18. this.setData({
19. imagewidth: imageSize.imageWidth,
20. imageheight: imageSize.imageHeight
21. })
22. }
23. })


 

 

3.util.js

1. //util.js
2. function imageUtil(e) {
3. var imageSize = {};
4. var originalWidth = e.detail.width;//图片原始宽
5. var originalHeight = e.detail.height;//图片原始高
6. var originalScale = originalHeight/originalWidth;//图片高宽比
7. console.log(‘originalWidth: ‘ + originalWidth)
8. console.log(‘originalHeight: ‘ + originalHeight)
9. //获取屏幕宽高
10. wx.getSystemInfo({
11. success: function (res) {
12. var windowWidth = res.windowWidth;
13. var windowHeight = res.windowHeight;
14. var windowscale = windowHeight/windowWidth;//屏幕高宽比
15. console.log(‘windowWidth: ‘ + windowWidth)
16. console.log(‘windowHeight: ‘ + windowHeight)
17. if(originalScale < windowscale){//图片高宽比小于屏幕高宽比
18. //图片缩放后的宽为屏幕宽
19. imageSize.imageWidth = windowWidth;
20. imageSize.imageHeight = (windowWidth * originalHeight) / originalWidth;
21. }else{//图片高宽比大于屏幕高宽比
22. //图片缩放后的高为屏幕高
23. imageSize.imageHeight = windowHeight;
24. imageSize.imageWidth = (windowHeight * originalWidth) / originalHeight;
25. }
27. }
28. })
29. console.log(‘缩放后的宽: ‘ + imageSize.imageWidth)
30. console.log(‘缩放后的高: ‘ + imageSize.imageHeight)
31. return imageSize;
32. }
34. module.exports = {
35. imageUtil: imageUtil
36. }