Trim functionality fails with error: Unexpected error while trimming. Try to lower the tolerance

In the latest version 0.21.3, trimming a png image fails. In a previous version 0.20.8, the code completes successfully.

Here’s my function in typescript:

async trim(dataUrl: string) {
    dataUrl = dataUrl.replace(/^data:image\/png;base64,/, "");
    dataUrl += dataUrl.replace('+', ' ');

    let buffer = new Buffer(dataUrl, "base64");

    return sharp(buffer)
        .png()
        .trim(1) //also tried default parameter
        .toBuffer();
}

This is the output in console: Error: Unexpected error while trimming. Try to lower the tolerance.

[lovell]

v0.23.3 now available, thank you for the original report.

[lovell]

All of the pixels in this image are black and the text is contained only in the transparency layer.

By default sharp/libvips flattens to black hence the entire image is background.

We need to retrieve the background colour from the bKGD chunk in the PNG, if present, and flatten to that instead.