node.js - Azure Functions，缩略图尺寸大于原始图像

Question

我用过这个Background image thumbnail processing with Azure Functions and NodeJS创建缩略图的文章。图像创建成功。但是图像的大小已增加。这是怎么回事？它一定很小吧？我该如何解决这个奇怪的问题？

这是 Blob 存储上的原始图像

处理后(缩略图)

这是 Azure 函数( Node ):

var Jimp = require("jimp");

module.exports = (context, myBlob) => {

    // Read image with Jimp
    Jimp.read(myBlob).then((image) => {

        // Manipulate image
        image
            .resize(200, Jimp.AUTO) 
            .greyscale()
            .getBuffer(Jimp.MIME_JPEG, (error, stream) => {

                // Check for errors
                if (error) {
                    context.log(`There was an error processing the image.`);
                    context.done(error);
                }
                else {
                    context.log(`Successfully processed the image`);

                    // Bind the stream to the output binding to create a new blob
                    context.done(null, stream);

                }

            });

    });

};

Answer 1

我已经找到了解决方案。

The default quality for JPEGs is 100. You should set this to something lower to gain compression:

您可以在这里阅读更多相关信息:Image is resized down and gets bigger file size

我必须设置.quality(50)，如下所示。此问题仅与JPEG有关。

var Jimp = require("jimp");

module.exports = (context, myBlob) => {

    // Read image with Jimp
    Jimp.read(myBlob).then((image) => {

        // Manipulate image
        image
            .resize(200, Jimp.AUTO)
            .greyscale()
            .quality(50) // set the quality for JPEGs
            .getBuffer(Jimp.MIME_JPEG, (error, stream) => {

                // Check for errors
                if (error) {
                    context.log(`There was an error processing the image.`);
                    context.done(error);
                }
                else {
                    context.log(`Successfully processed the image`);
                    // Bind the stream to the output binding to create a new blob
                    context.done(null, stream);

                }

            });

    });

};