How to efficiently implement the SVG water tower progress bar in the front-end mini program?

Mini Program SVG Water Tower Progress Bar: Detailed explanation of efficient implementation plan

This article discusses how to efficiently implement a dynamically changing SVG water tower progress bar in the applet environment and provides the best solution.

Objective: Create a water tower SVG graph whose water level is adjusted in real time according to the progress value. When the progress is below 20%, the water level will be red; otherwise it will be green. The water tower size must be adapted to the parent container size.

Two inefficient solutions:

1. Multi-picture switching scheme: Prepare multiple water tower pictures corresponding to different progress in advance, and display the progress by switching pictures. This solution package is large in size and has poor flexibility.
2. Image Clipping Scheme: Use two pictures to simulate water level changes through clip-path clip-cut upper pictures. However, the clip-path path is fixed, making it difficult to achieve adaptive adjustment.

Best solution: Directly operate SVG code

In the applet environment, the best solution is to directly operate the SVG code. The steps are as follows:

1. Read SVG files in binary: Use binary method to read SVG files to ensure that they are displayed correctly in iOS environment.
2. JavaScript dynamically modify SVG properties: find and replace the attribute values ​​in SVG that control water level height and color through JavaScript. For example, modify<rect ... height="104" width="64"></rect> height attribute value in the adjustment of the water level height, and fill attribute value is modified to change the color (less than 20% is red, otherwise it is green).
3. SVG to base64 encoding: convert the modified SVG code into a base64-encoded string.
4. Load to image tag: load base64 string to<image></image> Shown in the label.

Web-side development can directly use JavaScript variables to control SVG properties without base64 conversion.

The key is to find and modify the SVG attributes that control the height of the "mask". The SVG code examples provided by the article include height and color attributes, which developers can modify and adapt according to. This solution effectively avoids a large number of pictures, reduces the volume of the package, and realizes adaptive adjustment of the water tower size.

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