在将图像发送到服务器之前对其进行压缩

本文介绍了在将图像发送到服务器之前对其进行压缩的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在使用此代码将位图转换为 Base64 :

ByteArrayOutputStream baos = new ByteArrayOutputStream();bitmappress(Bitmap.CompressFormat.JPEG，** quality **，baos);byte [] b = baos.toByteArray();base64code = Base64.encodeToString(b，Base64.DEFAULT);

并通过以下方式在服务器端接收它:

$ strImage = preg_replace('！\ s *！'，''，trim($ this-> input-> post('image')));$ thefile = base64_decode($ strImage);$ img = imagecreatefromstring($ thefile);//header('Content-Type:image/jpeg');header('Content-Type:位图; charset = utf-8');imagesavealpha($ img，true);imagejpeg($ img，'./images/temp/testing.jpg'，100);imagedestroy($ img);

问题:

我从设备库中选择要发送到服务器的实际图像大小为 344 kb ，当我设置 quality = 0 并显示微调器对话框实用程序时 base64 字符串被发送到服务器需要花费 5秒的时间，并且服务器端收到的图像为 344 Kb ，但如果我将 quality = 100 设置为需要 60-70秒进行发送，而在服务器端收到的图像为 1.7 Mb

问题:

为什么我使用 quality = 0 时会得到实际尺寸，而当 quality = 100

时会比图像大近 5倍

注意:

当我设置 quality = 100 并进行更改

时

imagejpeg($ img，'./images/temp/testing.jpg'，100);

到

imagejpeg($ img，'./images/temp/testing.jpg'，10);

发送消息需要 60-70秒，但是服务器端接收到的图像太小 67 Kb

谢谢

解决方案

我认为@EJTH是正确的，因为0可能意味着完全不重新压缩图像.任何其他值(1-100)可能首先是将图像转换为位图(这将非常大)，然后压缩为目标质量jpeg.重新压缩需要花费一定的处理时间，因此您看到60到70秒(非0值)的时间.

我没有使用 Bitmap#compress 方法之前是这样，因此以上只是推测.

I am using this code to convert a Bitmap to Base64:

ByteArrayOutputStream baos = new ByteArrayOutputStream(); bitmappress(Bitmap.CompressFormat.JPEG, **quality**, baos); byte[] b = baos.toByteArray(); base64code = Base64.encodeToString(b, Base64.DEFAULT);

and receiving it at the server side, this way:

$strImage = preg_replace('!\s*!', '', trim($this->input->post('image'))); $thefile = base64_decode($strImage); $img = imagecreatefromstring($thefile); //header('Content-Type: image/jpeg'); header('Content-Type: bitmap; charset=utf-8'); imagesavealpha($img, true); imagejpeg($img,'./images/temp/testing.jpg',100); imagedestroy($img);

Problem:

The actual image size which i am picking from the device gallery to send to the server is 344 kb When i set the quality = 0 and show a spinner dialog util the base64 string is being sent to the server it takes 5 secs to send, and the image received at the server side is 344 Kb but if i am setting quality = 100 it takes 60-70 secs to send, and the image i receive at the server side is 1.7 Mb

Question:

why am i getting the actual size when using quality = 0 and nearly 5 times bigger image when quality = 100

Note:

When i am setting the quality = 100 and change

imagejpeg($img,'./images/temp/testing.jpg',100);

to

imagejpeg($img,'./images/temp/testing.jpg',10);

it takes 60-70 secs to send but the image received on the server side is too small 67 Kb

Thank You

解决方案

I would think that @EJTH is correct in that 0 might mean to not re-compress the image at all. Any other value (1-100) is probably first converting your image to a bitmap (which would be very large) then compressing to the target quality jpeg. This re-compression takes processing time to complete so you see 60-70 secs for values other than 0.

I've not used the Bitmap#compress method before though, so the above is speculation.