图片压缩，image.packing，怎么指定大小、宽高？

Question

上传头像的时候需要压缩图片，例如4000_3000的图片想要压缩到500_500，且大小在100kb以内

Answer 1

参考demo:

初始化图片资源到沙箱

async aboutToAppear\(\): Promise<void\> \{

const resourceManager = getContext\(this\).resourceManager

const imageArray = await resourceManager.getMediaContent\($r\('app.media.100'\)\);

console.log\("yuv\_path is:" + path\);

let file = fs.openSync\(path, fs.OpenMode.READ\_WRITE | fs.OpenMode.CREATE\);

fs.write\(file.fd, imageArray.buffer\).then\(\(writeLen\) =\> \{

console.info\("write data to file succeed and size is:" + writeLen\);

fs.closeSync\(file\);

\}\).catch\(\(err: BusinessError\) =\> \{

console.info\("write data to file failed with error message: " + err.message + ", error code: " + err.code\);

\}\);

\}

创建pixelMap，并调用压缩方法

/ // path为已获得的沙箱路径

const imageSource: image.ImageSource = image.createImageSource\(path\);

//创建pixelMap

this.pixelMap = await imageSource.createPixelMap\(decodingOptions\);

console.log\("6666661" + this.pixelMap.getPixelBytesNumber\(\)\);

//指定压缩宽、高、大小

this.packingDetail\(500, 500, 100\)

根据压缩后目标图片宽高计算缩放比 并进行缩放，调用packing方法实现第一次压缩

if \(this.pixelMap\) \{

Logger.info\("zhaohao before scaling pixelmap." + this.pixelMap.getPixelBytesNumber\(\)\);

let imageInfo = await this.pixelMap.getImageInfo\(\);

let a = this.pixelMap

//计算压缩比

let scaleX: number = targetWidth / imageInfo.size.width;

let scaleY: number = targetHeight / imageInfo.size.height;

this.pixelMap.scale\(scaleX, scaleY, \(err: BusinessError\) =\> \{

if \(err\) \{

console.error\("zhaohao Failed to scale pixelmap."\);

return;

\} else \{

console.log\("zhaohao in scaling pixelmap." + a.getPixelBytesNumber\(\)\);

\}

\}\);

\}

let imagePackerApi = image.createImagePacker\(\);

let packOpts: image.PackingOption = \{ format: "image/jpeg", quality: 100 \};

imagePackerApi.packing\(this.pixelMap, packOpts\).then\(\(data: ArrayBuffer\) =\> \{

Logger.info\("zhaohao in 100 quality data" + data.byteLength\)

this.compressPictures\(data, targetPixelSize, 99\);

\}\);

调用递归算法，当压缩后的data ，小于等于压缩目标图片大小时将data写入本地沙箱并结束递归

compressPictures\(data?: ArrayBuffer, size?: number, quality?: number\): void \{

if \(data && size && quality\) \{

const currentSize = data.byteLength / 1024

if \(currentSize <= size || quality === 0\) \{

console.log\("finally quallity is:" + ++quality\)

let file = fs.openSync\(path9, fs.OpenMode.READ\_WRITE | fs.OpenMode.CREATE\);

fs.write\(file.fd, data\).then\(async \(writeLen\) =\> \{

console.info\("write data to file succeed2 and size is:" + writeLen\);

fs.closeSync\(file\);

\}\).catch\(\(err: BusinessError\) =\> \{

console.info\("write data to file failed1 with error message: " + err.message + ", error code: " + err.code\);

\}\);

return;

\}

\}

if \(quality\) \{

let packOpts: image.PackingOption = \{ format: "image/jpeg", quality: quality \}

let imagePackerApi = image.createImagePacker\(\);

imagePackerApi.packing\(this.pixelMap, packOpts\)

.then\(\(ret: ArrayBuffer\) =\> \{

//递归算法，直到压缩到指定大小的data

if \(quality\) \{

Logger.info\("PACKING66666"+quality\)

return this.compressPictures\(ret, size, quality - 1\)

\}

\}\).catch\(\(err: BusinessError\) =\> \{

console.log\(\`lbh\`\)

return false

\}\)

\}

\}