zlib

What can be the least possible value of data-compression-ratio for any real dataset

由 ぃ、小莉子 提交于 2019-12-24 05:18:04
问题 I am writing ZLIB like API for an embedded hardware compressor which uses deflate algorithm for compression of given input stream. Before going further i would like to explain data compression ratio. Data compression ratio is defined as the ratio between the uncompressed size and compressed size. Compression ratio is usually greater than one. which mean compressed data is usually smaller than uncompressed data, which is whole point to do compression. but this is not always the case. for

Error: incorrect header check at Zlib._handle.onerror (zlib.js:355:17) errno: -3, code: 'Z_DATA_ERROR'

由 纵饮孤独 提交于 2019-12-24 01:49:08
问题 My HTTP request has {'content-encoding': "gzip"} header. I am trying to read the data using node.js. I use below code to decompress the data. But i get Error: incorrect header check at Zlib._handle.onerror (zlib.js:355:17) errno: -3, code: 'Z_DATA_ERROR'. Can somebody help me to rectify this error. var myHttp = require("http"); var url = require("url"); var qString = require("querystring"); var fs = require('fs'); var zlib = require('zlib'); var myEvents = require('./customEvents'); var

How to decompress stream deflated with java.util.zip.Deflater in .NET?

由 安稳与你 提交于 2019-12-23 19:07:08
问题 I have a dump after java.util.zip.Deflater (can confirm it's valid because Java's Inflater opens it fine) and need to open it in .NET: byte[] content = ReadSample(sampleName); var input = new MemoryStream(content); var output = new MemoryStream(); using (var z = new System.IO.Compression.DeflateStream(input, CompressionMode.Decompress, true)) z.CopyTo(output); This throws System.IO.InvalidDataException : Block length does not match with its complement. Tried Ionic.Zlib.DeflateStream - similar

How to use crc32 from zlib in swift (Xcode 9)

由 我是研究僧i 提交于 2019-12-23 17:38:17
问题 I'm new to swift/xcode and am trying to use the crc32 function that, as mentioned here, is provided in zlib from libz.dylib . I've modified the code so that I am now trying: let message1 = "some message".first?.value!.data(using: String.Encoding.utf8, allowLossyConversion: false) let crc = crc32(CLong(0), UnsafePointer<Bytef>(strcat!.bytes), UInt(message1!.length)) however I am encountering the error: use of unresolved identifier 'crc32' . Could anyone help me to figure out what step I might

How can I decrease the amount of time it takes to save a png using QImage?

由 蹲街弑〆低调 提交于 2019-12-23 12:28:52
问题 Using Qt 4.8rc1, I have a QImage that I want to convert to a png file. It seems like it is taking longer than it should to convert to png format: ~70ms for an 800x800 empty png. Is there a way I can make this more efficient, or am I just inherently limited by png/zlib? Here is the benchmark I am running: #include <QtGui> #include <QTimer> int main(int argc, char *argv[]) { int times = 1000; QString format("png"); QByteArray ba; QBuffer* buffer = new QBuffer(&ba); buffer->open(QIODevice:

CentOS 6.5 编译安装 LNMP环境

由 喜夏-厌秋 提交于 2019-12-23 12:27:19
具体参考： http://www.centoscn.com/CentosServer/www/2015/0422/5245.html http://www.cnblogs.com/zhoulf/archive/2013/02/09/2909653.html 建立一个软件包目录存放 mkdir -p /usr/local/src/ 清理已经安装包 rpm -e httpd rpm -e mysql rpm -e php yum -y remove httpd yum -y remove mysql yum -y remove php #搜索apache包 rpm -qa http* #强制卸载apache包 rpm -e --nodeps 查询出来的文件名 #检查是否卸载干净 rpm -qa|grep http* selinux可能会致使编译安装失败，我们先禁用它。永久禁用，需要重启生效 sed -i 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/selinux/config 临时禁用，不需要重启 setenforce 0 安装必备工具 yum -y install make gcc gcc-c++ gcc-g77 flex bison file libtool libtool-libs autoconf kernel-devel

boost::iostream zlib compressing multiple files into one archive

由 空扰寡人 提交于 2019-12-23 08:38:11
问题 i'm having trouble packing a bunch of files into one archive. the boost docs are very limited on this topic and i've searched the web for several hours now, but i can't find a solution. What i have so far: boost::filesystem::ofstream ofsArchive("some.zip"); boost::iostreams::filtering_ostreambuf outFilter; boost::iostreams::zlib_params zparam(boost::iostreams::zlib::default_compression); try { // set up the filter outFilter.strict_sync(); outFilter.push(boost::iostreams::zlib_compressor

Using zlib deflateBound() dynamically

由 瘦欲@ 提交于 2019-12-23 04:59:10
问题 I have been looking at how to use deflateBound() dynamically and have not found exactly what I am looking for. I looked at the manual for zlip, examples included in library and found these here: Compression Libraries for ARM Cortex M3/4 Determine compressed/uncompressed buffer size for Z-lib in C zlib, deflate: How much memory to allocate? What I am missing is how to allocate after calling deflateBound(). E.g. this looks like it will cause problems z_stream defstream; uint8_t *outBuf=NULL;

Native Swift implementation of DEFLATE (unzip) algorithm [closed]

由 不想你离开。 提交于 2019-12-23 03:42:19
问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 2 years ago . I have some data that has been compressed with the DEFLATE algorithm which I believe is basically just saying its zipped up. I'm writing a swift app and I was interested in figuring out if there is a native pure swift (2.0) implementation of the unzip algorithm. I need to implement this in a swift dynamic

Ubuntu搭建face_recognition环境

由 感情迁移 提交于 2019-12-23 03:39:39
https://github.com/ageitgey/face_recognition/blob/master/README_Simplified_Chinese.md https://gist.github.com/ageitgey/629d75c1baac34dfa5ca2a1928a7aeaf ubunt18.04 apt-get update -y apt-get upgrade -y apt install git sudo apt-get install git $ git --version apt-get install build-essential sudo apt-get install ia32-libs apt-get install cmake $ /usr/bin/c++ --version cmake --version cmake version 3.10.2 git clone https://github.com/davisking/dlib.git cd dlib mkdir build; cd build; cmake ..; cmake --build . 等待...... root@opencv-learn-pc2:~# cd dlib/ root@opencv-learn-pc2:~/dlib# ls build dlib
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