because the image is loaded asynchronously, you need to make sure that your image has been loaded and then rendered to canvas, you can try img.onload this method. (if canvas wants to render multiple pictures, it is recommended that you consider the counter implementation. Use the toDataUrl method when the count reaches a certain point. The personal test is valid, hee hee)

some colleagues seem to have encountered a similar problem before, and the solution is to remove data:image/png;base64.