deflate

问题 I want to use gzip or deflate compression on outgoing POST and PUT JSON requests to an API project from an Angular 4 application. Presently, I'm using HttpClient to send the requests. I've tried using pako or zlib to generate the compressed content, but the server returns back responses indicating a bad implementation of the compression algorithm. My POST TypeScript looks like the following: public post(url: string, content: any): Observable < any > { const fullUrl: string = `${HttpService

问题 I'm currently in the middle of writing a small PNG image I/O library myself for learning purposes. My problem is the following: I created a small PNG only 2 by 2 pixels in dimension and opened it in a hex editor to study its contents. This is the image I created using GIMP and stored with a compression of "9". (Please note that this is an enlarged image of the original 2 by 2 pixel image ;) ) So I guess uncompressed, this would look something like this in memory: 00 00 00 FF 00 00 00 00 FF 00

问题 I use following .htaccess to set gzip compression: AddOutputFilterByType DEFLATE text/html image/png image/jpeg text/css text/javascript Please check this url: http://www.coinex.com/cn/silver_panda/proof/china_1984_27_gram_silver_panda_coin/ the gzip compression works for html, css, js and jpg, but not working for png (really amazing..) 回答1: PNG is already a compressed data format. Compressing it with GZIP is not likely to decrease the size, and can in fact make it larger. I'm surprised you

问题 Zlib can output three format, I try to search the docs and zlib.h , but can't find a clear explanation about the options, anyone have any ideas? 回答1: From the zlib.h documentation of deflateInit2() : windowBits can also be -8..-15 for raw deflate. In this case, -windowBits determines the window size. deflate() will then generate raw deflate data with no zlib header or trailer, and will not compute a check value. windowBits can also be greater than 15 for optional gzip encoding. Add 16 to

问题 Zlib can output three format, I try to search the docs and zlib.h , but can't find a clear explanation about the options, anyone have any ideas? 回答1: From the zlib.h documentation of deflateInit2() : windowBits can also be -8..-15 for raw deflate. In this case, -windowBits determines the window size. deflate() will then generate raw deflate data with no zlib header or trailer, and will not compute a check value. windowBits can also be greater than 15 for optional gzip encoding. Add 16 to

问题 What does a zipped html file using zlib (deflate) look like sitting on the server? Does it have a different extension than .html? 回答1: Depending on your webserver settings, it is also possible to zip the html files in advance, in addition to having the webserver automatically zip them. Usually the extension is .gz, eg MyPage.html becomes MyPage.html.gz. With the right settings, if someone requests http://example.com/MyPage.html, and Apache sees MyPage.html.gz, and the client supports

问题 I'm trying to extract data from compressed bytes from network capture file (PCAP.) Data from some of these packets don't have ZLIB header (the first 2 bytes, where lower 4 bits of first byte is always 8) and hence gave exception when I tried to decompress it using ZlibStream . Data with headers seem to work fine. As I understand that ZLIB is just a header and footer over DEFLATE, I pass these data without headers to DeflateStream . This time DeflateStream doesn't throw any error, it just gave

问题 It's well known that GZIP or DEFLATE (or any compression mechanism) can increase file size sometimes. Is there a maximum (either percentage or constant) that a file can be increased? What is it? If a file is X bytes, and I'm going to gzip it, and I need to budget for file space in advance - what's the worst case scenario? UPDATE: There are two overheads: GZIP adds a header, typically 18 bytes but essentially arbitrarily long. What about DEFLATE? That can expand content by a multiplicative

问题 Testing different possibilities to download the source of a webpage I got the following results (Average time in ms to google.com, 9gag.com): Plain HttpWebRequest: 169, 360 Gzip HttpWebRequest: 143, 260 WebClient GetStream : 132 , 295 WebClient DownloadString: 143, 389 So for my 9gag client I decided to take the gzip HttpWebRequest. The problem is, after implementing in my actual program, the request takes more than twice the time. The Problem also occurs when just adding a Thread.Sleep

问题 We recently switched some of our sites from deflate to gzip and noticed a significant increase in cpu load on our servers. 回答1: Is it possible that you are experiencing cache miss? That is, compressed content is sometimes cached compressed but switching compression schemes would (or at least should) invalidate that cache causing dramatically increased cpu utilization. Did you try switching it back? 回答2: gzip is, basically, deflate with some additional headers. So there should not be a