libpng | 易学教程

Obtain text fields from a png file

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问题 Nothing seems to work so far. I got to see with pnginfo the following message: concept_Sjet_dream6.png... Image Width: 200 Image Length: 240 Bitdepth (Bits/Sample): 8 Channels (Samples/Pixel): 2 Pixel depth (Pixel Depth): 16 Colour Type (Photometric Interpretation): GRAYSCALE with alpha channel Image filter: Single row per byte filter Interlacing: No interlacing Compression Scheme: Deflate method 8, 32k window Resolution: 11811, 11811 (pixels per meter) FillOrder: msb-to-lsb Byte Order:

Linker error with libpng under MacOSX

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问题 I'm working on MacOSX 10.7.2 and Xcode 4.2.1. I installed libpng using port and I was trying to load a PNG image in my application, but I get linker errors: Undefined symbols for architecture x86_64: "_png_create_read_struct", referenced from: loadPngImage(char*, int&, int&, bool&, unsigned char**) in test.o "_png_create_info_struct", referenced from: loadPngImage(char*, int&, int&, bool&, unsigned char**) in test.o "_png_destroy_read_struct", referenced from: loadPngImage(char*, int&, int&,

Linux编译安装Apache+PHP

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Linux编译安装Apache+PHP 来自：自学it网， http://www.zixue.it/ 。 1 】编译安装 Apache+PHP 1. 安装程序依赖库和开发环境为了省事把所需要的库文件全都安装上，可以使用rpm包安装，也可以用yum命令安装， yum -y install gcc gcc-c++ autoconf automake make libjpeg libjpeg-devel libxml2 libxml2-devel zlib zlib-devel glibc glibc-devel glib2 glib2-devel bzip2 bzip2-devel ncurses ncurses-devel curl curl-devel e2fsprogs e2fsprogs-devel krb5 krb5-devel libidn libidn-devel openssl openssl-devel openldap openldap-devel nss_ldap openldap-clients openldap-servers libtool* mysql-devel ln -s /usr/lib64/mysql/libmysqlclient.so.16.0.0 /usr/lib/libmysqlclient_r.so 2. 部署 apache (1) 解包

linux下编译安装Apache+PHP

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1.安装程序依赖库和开发环境在编译安装apache和php之前，首先把安装需要依赖的库文件安装好： yum -y install gcc gcc-c++ autoconf automake make libjpeg libjpeg-devel libxml2 libxml2-devel zlib zlib-devel glibc glibc-devel glib2 glib2-devel bzip2 bzip2-devel ncurses ncurses-devel curl curl-devel e2fsprogs e2fsprogs-devel krb5 krb5-devel libidn libidn-devel openssl openssl-devel openldap openldap-devel nss_ldap openldap-clients openldap-servers libtool* mysql-devel ln -s /usr/lib64/mysql/libmysqlclient.so.16.0.0 /usr/lib/libmysqlclient_r.so 2.部署apache (1)解包 tar zxvf httpd-2.2.34.tar.gz (2)切换目录 cd ttpd-2.2.34 (3)配置 ./configure --prefix=

Crash in png_set_read_fn() on Windows 7

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问题 I'm cross-compiling some C code for Windows 7 and linking to libpng12.dll found here. Unfortunately, the line below causes a crash (GDB says segmentation fault): png_structp png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL); I'm not sure where to start to debug this--that function seems very straightforward and unrelated to the rest of the code. Top of the backtrace looks like this: #0 0xabababab in ?? () #1 0x6cc556d1 in png_set_read_fn () from c:\...libpng12.dll #2

libpng: write a bigger png than 1002px

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问题 I'm currently writing a c++ program which should write me a png file as output. So I made a little code, actually works. I just took the source code from here and condesed it. My code is nopasted here. BUT: It only works if it doesn't exceed 1002 pixels in width. I am very sure the problem is somewhere around lines 29/30, so a malloc problem, but I don't get it. Thanks for your help & greez 回答1: Without diving into the code too deeply, there are these interesting constants: unsigned width =

graphicsmagick is doubling the size of “some” PNG files

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问题 Using GraphicsMagick to read in a PNG file and write it out under a different name is causing the file size to increase by more than double. This only happens to some PNG files and I can't figure out what is causing it. Example problem PNG: http://www.google.co.in/logos/2011/verne-hp-3.png I have tried everything from disabling the opacity channel to using different compression types to changing the interlacing type but nothing is helping me understand what is causing this problem. If anyone

Building a fast PNG encoder issues

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问题 I am trying to build a fast 8-bit greyscale PNG encoder. Unfortunately I must be misunderstanding part of the spec. Smaller image sizes seem to work, but the larger ones will only open in some image viewers. This image (with multiple DEFLATE Blocks) gives a "Decompression error in IDAT" error in my image viewer but opens fine in my browser: This image has just one DEFLATE block but also gives an error: Below I will outline what I put in my IDAT chunk in case you can easily spot any mistakes

Libpng conflict on OpenCV?

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问题 I am trying to open up png files on my XCode 4.4 (Mountain Lion) with the following codes (works for jpg files) Mat image = imread( "/Users/user_name/Desktop/result.png" ); imshow( "", image ); waitKey( 0 ); But OpenCV throws me this error: libpng warning: Application built with libpng-1.4.12 but running with 1.5.4 OpenCV Error: Bad flag (parameter or structure field) (Unrecognized or unsupported array type) in cvGetMat, file /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync

Qt Creator failed on running program when linking /usr/local/lib

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问题 Given the following simple project: QT += core QT -= gui TARGET = ConsoleTest08 CONFIG += console CONFIG -= app_bundle TEMPLATE = app SOURCES += main.cpp LIBS += -L/usr/local/lib With this simple main.cpp file: int main(int argc, char *argv[]) { return 0; } When running from Qt Creator , I have the following error: dyld: Symbol not found: __cg_png_create_info_struct Referenced from: /System/Library/Frameworks/ImageIO.framework/Versions/A/ImageIO Expected in: /usr/local/lib/libPng.dylib in