一、库的编译
1、下载 libjpeg 源码，这里我下载的是 jpegsr9e.zip
2、解压源码
3、进入解压后的目录，找到 makefile.vs 文件,用文本编辑器打开并编辑，找到 语句
#!include <win32.mak>
所在行，并将 win32.mak 替换为实际位置, 我这边修改后的值为
!include <C:\Program Files (x86)\Microsoft SDKs\Windows\v7.1A\Include\win32.mak>
4、在文件中查找关键字 “setup”， 这个是我们后面生成vs 工程文件要用到的，我这边带有关键字“setup” 的有
setup-vc6:
setupcopy-vc6:
setup-v16:
setupcopy-v16:
setup-v17:
setupcopy-v17:
上面的 setup-vc6 就表示 vc++ 6.0 编译器
setup-vc16 就表示 vs2019 编译器，后面的以此类推，自己是什么编译器就对应那个关键句
5、生成 sln 工程文件:在电脑的 “开始”菜单中，找到 vs2019的命令行工具，并打开，我这里是
x86 Native Tools Command Prompt for VS 2019
打开后，会出来一个命令行界面，在里面进入 libjeg 源码所在目录，并输入一下命令来生成vs 的工程文件
NMAKE /f makefile.vc setup-v16
如果提示找不到 jconfig.h文件的话，就复制一份 jconfig.vc 改名成 jconfig.h
而后，继续执行上面的nmake命令
执行成功后，会在当前目录下生成一个 .sln 的工程文件，打开这个 sln 文件，正常编译即可，默认是编译静态库，编译出来是一个 jpeg.lib 文件。
二、编译动态库
1、在上一步的基础上，在工程中新建c++ 头文件 jexport.h，里面输入的内容如下
#pragma once
#if defined(_WIN32)
# if defined(LIBJPEG_STATIC)
# define LIBJPEG_EXPORT_API
# else
# if defined(LIBJPEG_EXPORTS)
# define LIBJPEG_EXPORT_API __declspec(dllexport)
# else
# define LIBJPEG_EXPORT_API __declspec(dllimport)
# endif
# endif
#else
# define LIBJPEG_EXPORT_API
#endif
2、修改 jmorecfg.h 文件:
在文件开始处添加 jexport.h 的引用, 找到语句
#define EXTERN(type)
并修改为
#define EXTERN(type) extern LIBJPEG_EXPORT_API type
我这边修改后的文件为
/*
* jmorecfg.h
*
* Copyright (C) 1991-1997, Thomas G. Lane.
* Modified 1997-2013 by Guido Vollbeding.
* This file is part of the Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*
* This file contains additional configuration options that customize the
* JPEG software for special applications or support machine-dependent
* optimizations. Most users will not need to touch this file.
*/
#include "jexport.h"
/*
* Define BITS_IN_JSAMPLE as either
* 8 for 8-bit sample values (the usual setting)
* 9 for 9-bit sample values
* 10 for 10-bit sample values
* 11 for 11-bit sample values
* 12 for 12-bit sample values
* Only 8, 9, 10, 11, and 12 bits sample data precision are supported for
* full-feature DCT processing. Further depths up to 16-bit may be added
* later for the lossless modes of operation.
* Run-time selection and conversion of data precision will be added later
* and are currently not supported, sorry.
* Exception: The transcoding part (jpegtran) supports all settings in a
* single instance, since it operates on the level of DCT coefficients and
* not sample values. The DCT coefficients are of the same type (16 bits)
* in all cases (see below).
*/
#define BITS_IN_JSAMPLE 8 /* use 8, 9, 10, 11, or 12 */
/*
* Maximum number of components (color channels) allowed in JPEG image.
* To meet the letter of the JPEG spec, set this to 255. However, darn
* few applications need more than 4 channels (maybe 5 for CMYK + alpha
* mask). We recommend 10 as a reasonable compromise; use 4 if you are
* really short on memory. (Each allowed component costs a hundred or so
* bytes of storage, whether actually used in an image or not.)
*/
#define MAX_COMPONENTS 10 /* maximum number of image components */
/*
* Basic data types.
* You may need to change these if you have a machine with unusual data
* type sizes; for example, "char" not 8 bits, "short" not 16 bits,
* or "long" not 32 bits. We don't care whether "int" is 16 or 32 bits,
* but it had better be at least 16.
*/
/* Representation of a single sample (pixel element value).
* We frequently allocate large arrays of these, so it's important to keep
* them small. But if you have memory to burn and access to char or short
* arrays is very slow on your hardware, you might want to change these.
*/
#if BITS_IN_JSAMPLE == 8
/* JSAMPLE should be the smallest type that will hold the values 0..255.
* You can use a signed char by having GETJSAMPLE mask it with 0xFF.
*/
#ifdef HAVE_UNSIGNED_CHAR
typedef unsigned char JSAMPLE;
#define GETJSAMPLE(value) ((int) (value))
#else /* not HAVE_UNSIGNED_CHAR */
typedef char JSAMPLE;
#ifdef CHAR_IS_UNSIGNED
#define GETJSAMPLE(value) ((int) (value))
#else
#define GETJSAMPLE(value) ((int) (value) & 0xFF)
#endif /* CHAR_IS_UNSIGNED */
#endif /* HAVE_UNSIGNED_CHAR */
#define MAXJSAMPLE 255
#define CENTERJSAMPLE 128
#endif /* BITS_IN_JSAMPLE == 8 */
#if BITS_IN_JSAMPLE == 9
/* JSAMPLE should be the smallest type that will hold the values 0..511.
* On nearly all machines "short" will do nicely.
*/
typedef short JSAMPLE;
#define GETJSAMPLE(value) ((int) (value))
#define MAXJSAMPLE 511
#define CENTERJSAMPLE 256
#endif /* BITS_IN_JSAMPLE == 9 */
#if BITS_IN_JSAMPLE == 10
/* JSAMPLE should be the smallest type that will hold the values 0..1023.
* On nearly all machines "short" will do nicely.
*/
typedef short JSAMPLE;
#define GETJSAMPLE(value) ((int) (value))
#define MAXJSAMPLE 1023
#define CENTERJSAMPLE 512
#endif /* BITS_IN_JSAMPLE == 10 */
#if BITS_IN_JSAMPLE == 11
/* JSAMPLE should be the smallest type that will hold the values 0..2047.
* On nearly all machines "short" will do nicely.
*/
typedef short JSAMPLE;
#define GETJSAMPLE(value) ((int) (value))
#define MAXJSAMPLE 2047
#define CENTERJSAMPLE 1024
#endif /* BITS_IN_JSAMPLE == 11 */
#if BITS_IN_JSAMPLE == 12
/* JSAMPLE should be the smallest type that will hold the values 0..4095.
* On nearly all machines "short" will do nicely.
*/
typedef short JSAMPLE;
#define GETJSAMPLE(value) ((int) (value))
#define MAXJSAMPLE 4095
#define CENTERJSAMPLE 2048
#endif /* BITS_IN_JSAMPLE == 12 */
/* Representation of a DCT frequency coefficient.
* This should be a signed value of at least 16 bits; "short" is usually OK.
* Again, we allocate large arrays of these, but you can change to int
* if you have memory to burn and "short" is really slow.
*/
typedef short JCOEF;
/* Compressed datastreams are represented as arrays of JOCTET.
* These must be EXACTLY 8 bits wide, at least once they are written to
* external storage. Note that when using the stdio data source/destination
* managers, this is also the data type passed to fread/fwrite.
*/
#ifdef HAVE_UNSIGNED_CHAR
typedef unsigned char JOCTET;
#define GETJOCTET(value) (value)
#else /* not HAVE_UNSIGNED_CHAR */
typedef char JOCTET;
#ifdef CHAR_IS_UNSIGNED
#define GETJOCTET(value) (value)
#else
#define GETJOCTET(value) ((value) & 0xFF)
#endif /* CHAR_IS_UNSIGNED */
#endif /* HAVE_UNSIGNED_CHAR */
/* These typedefs are used for various table entries and so forth.
* They must be at least as wide as specified; but making them too big
* won't cost a huge amount of memory, so we don't provide special
* extraction code like we did for JSAMPLE. (In other words, these
* typedefs live at a different point on the speed/space tradeoff curve.)
*/
/* UINT8 must hold at least the values 0..255. */
#ifdef HAVE_UNSIGNED_CHAR
typedef unsigned char UINT8;
#else /* not HAVE_UNSIGNED_CHAR */
#ifdef CHAR_IS_UNSIGNED
typedef char UINT8;
#else /* not CHAR_IS_UNSIGNED */
typedef short UINT8;
#endif /* CHAR_IS_UNSIGNED */
#endif /* HAVE_UNSIGNED_CHAR */
/* UINT16 must hold at least the values 0..65535. */
#ifdef HAVE_UNSIGNED_SHORT
typedef unsigned short UINT16;
#else /* not HAVE_UNSIGNED_SHORT */
typedef unsigned int UINT16;
#endif /* HAVE_UNSIGNED_SHORT */
/* INT16 must hold at least the values -32768..32767. */
#ifndef XMD_H /* X11/xmd.h correctly defines INT16 */
typedef short INT16;
#endif
/* INT32 must hold at least signed 32-bit values. */
#ifndef XMD_H /* X11/xmd.h correctly defines INT32 */
#ifndef _BASETSD_H_ /* Microsoft defines it in basetsd.h */
#ifndef _BASETSD_H /* MinGW is slightly different */
#ifndef QGLOBAL_H /* Qt defines it in qglobal.h */
typedef long INT32;
#endif
#endif
#endif
#endif
/* Datatype used for image dimensions. The JPEG standard only supports
* images up to 64K*64K due to 16-bit fields in SOF markers. Therefore
* "unsigned int" is sufficient on all machines. However, if you need to
* handle larger images and you don't mind deviating from the spec, you
* can change this datatype.
*/
typedef unsigned int JDIMENSION;
#define JPEG_MAX_DIMENSION 65500L /* a tad under 64K to prevent overflows */
/* These macros are used in all function definitions and extern declarations.
* You could modify them if you need to change function linkage conventions;
* in particular, you'll need to do that to make the library a Windows DLL.
* Another application is to make all functions global for use with debuggers
* or code profilers that require it.
*/
/* a function called through method pointers: */
#define METHODDEF(type) static type
/* a function used only in its module: */
#define LOCAL(type) static type
/* a function referenced thru EXTERNs: */
#define GLOBAL(type) type
/* a reference to a GLOBAL function: */
//#define EXTERN(type) extern type
#define EXTERN(type) extern LIBJPEG_EXPORT_API type
/* This macro is used to declare a "method", that is, a function pointer.
* We want to supply prototype parameters if the compiler can cope.
* Note that the arglist parameter must be parenthesized!
* Again, you can customize this if you need special linkage keywords.
*/
#ifdef HAVE_PROTOTYPES
#define JMETHOD(type,methodname,arglist) type (*methodname) arglist
#else
#define JMETHOD(type,methodname,arglist) type (*methodname) ()
#endif
/* The noreturn type identifier is used to declare functions
* which cannot return.
* Compilers can thus create more optimized code and perform
* better checks for warnings and errors.
* Static analyzer tools can make improved inferences about
* execution paths and are prevented from giving false alerts.
*
* Unfortunately, the proposed specifications of corresponding
* extensions in the Dec 2011 ISO C standard revision (C11),
* GCC, MSVC, etc. are not viable.
* Thus we introduce a user defined type to declare noreturn
* functions at least for clarity. A proper compiler would
* have a suitable noreturn type to match in place of void.
*/
#ifndef HAVE_NORETURN_T
typedef void noreturn_t;
#endif
/* Here is the pseudo-keyword for declaring pointers that must be "far"
* on 80x86 machines. Most of the specialized coding for 80x86 is handled
* by just saying "FAR *" where such a pointer is needed. In a few places
* explicit coding is needed; see uses of the NEED_FAR_POINTERS symbol.
*/
#ifndef FAR
#ifdef NEED_FAR_POINTERS
#define FAR far
#else
#define FAR
#endif
#endif
/*
* On a few systems, type boolean and/or its values FALSE, TRUE may appear
* in standard header files. Or you may have conflicts with application-
* specific header files that you want to include together with these files.
* Defining HAVE_BOOLEAN before including jpeglib.h should make it work.
*/
#ifndef HAVE_BOOLEAN
#if defined FALSE || defined TRUE || defined QGLOBAL_H
/* Qt3 defines FALSE and TRUE as "const" variables in qglobal.h */
typedef int boolean;
#ifndef FALSE /* in case these macros already exist */
#define FALSE 0 /* values of boolean */
#endif
#ifndef TRUE
#define TRUE 1
#endif
#else
typedef enum { FALSE = 0, TRUE = 1 } boolean;
#endif
#endif
/*
* The remaining options affect code selection within the JPEG library,
* but they don't need to be visible to most applications using the library.
* To minimize application namespace pollution, the symbols won't be
* defined unless JPEG_INTERNALS or JPEG_INTERNAL_OPTIONS has been defined.
*/
#ifdef JPEG_INTERNALS
#define JPEG_INTERNAL_OPTIONS
#endif
#ifdef JPEG_INTERNAL_OPTIONS
/*
* These defines indicate whether to include various optional functions.
* Undefining some of these symbols will produce a smaller but less capable
* library. Note that you can leave certain source files out of the
* compilation/linking process if you've #undef'd the corresponding symbols.
* (You may HAVE to do that if your compiler doesn't like null source files.)
*/
/* Capability options common to encoder and decoder: */
#define DCT_ISLOW_SUPPORTED /* slow but accurate integer algorithm */
#define DCT_IFAST_SUPPORTED /* faster, less accurate integer method */
#define DCT_FLOAT_SUPPORTED /* floating-point: accurate, fast on fast HW */
/* Encoder capability options: */
#define C_ARITH_CODING_SUPPORTED /* Arithmetic coding back end? */
#define C_MULTISCAN_FILES_SUPPORTED /* Multiple-scan JPEG files? */
#define C_PROGRESSIVE_SUPPORTED /* Progressive JPEG? (Requires MULTISCAN)*/
#define DCT_SCALING_SUPPORTED /* Input rescaling via DCT? (Requires DCT_ISLOW)*/
#define ENTROPY_OPT_SUPPORTED /* Optimization of entropy coding parms? */
/* Note: if you selected more than 8-bit data precision, it is dangerous to
* turn off ENTROPY_OPT_SUPPORTED. The standard Huffman tables are only
* good for 8-bit precision, so arithmetic coding is recommended for higher
* precision. The Huffman encoder normally uses entropy optimization to
* compute usable tables for higher precision. Otherwise, you'll have to
* supply different default Huffman tables.
* The exact same statements apply for progressive JPEG: the default tables
* don't work for progressive mode. (This may get fixed, however.)
*/
#define INPUT_SMOOTHING_SUPPORTED /* Input image smoothing option? */
/* Decoder capability options: */
#define D_ARITH_CODING_SUPPORTED /* Arithmetic coding back end? */
#define D_MULTISCAN_FILES_SUPPORTED /* Multiple-scan JPEG files? */
#define D_PROGRESSIVE_SUPPORTED /* Progressive JPEG? (Requires MULTISCAN)*/
#define IDCT_SCALING_SUPPORTED /* Output rescaling via IDCT? (Requires DCT_ISLOW)*/
#define SAVE_MARKERS_SUPPORTED /* jpeg_save_markers() needed? */
#define BLOCK_SMOOTHING_SUPPORTED /* Block smoothing? (Progressive only) */
#undef UPSAMPLE_SCALING_SUPPORTED /* Output rescaling at upsample stage? */
#define UPSAMPLE_MERGING_SUPPORTED /* Fast path for sloppy upsampling? */
#define QUANT_1PASS_SUPPORTED /* 1-pass color quantization? */
#define QUANT_2PASS_SUPPORTED /* 2-pass color quantization? */
/* more capability options later, no doubt */
/*
* Ordering of RGB data in scanlines passed to or from the application.
* If your application wants to deal with data in the order B,G,R, just
* change these macros. You can also deal with formats such as R,G,B,X
* (one extra byte per pixel) by changing RGB_PIXELSIZE. Note that changing
* the offsets will also change the order in which colormap data is organized.
* RESTRICTIONS:
* 1. The sample applications cjpeg,djpeg do NOT support modified RGB formats.
* 2. The color quantizer modules will not behave desirably if RGB_PIXELSIZE
* is not 3 (they don't understand about dummy color components!). So you
* can't use color quantization if you change that value.
*/
#define RGB_RED 0 /* Offset of Red in an RGB scanline element */
#define RGB_GREEN 1 /* Offset of Green */
#define RGB_BLUE 2 /* Offset of Blue */
#define RGB_PIXELSIZE 3 /* JSAMPLEs per RGB scanline element */
/* Definitions for speed-related optimizations. */
/* If your compiler supports inline functions, define INLINE
* as the inline keyword; otherwise define it as empty.
*/
#ifndef INLINE
#ifdef __GNUC__ /* for instance, GNU C knows about inline */
#define INLINE __inline__
#endif
#ifndef INLINE
#define INLINE /* default is to define it as empty */
#endif
#endif
/* On some machines (notably 68000 series) "int" is 32 bits, but multiplying
* two 16-bit shorts is faster than multiplying two ints. Define MULTIPLIER
* as short on such a machine. MULTIPLIER must be at least 16 bits wide.
*/
#ifndef MULTIPLIER
#define MULTIPLIER int /* type for fastest integer multiply */
#endif
/* FAST_FLOAT should be either float or double, whichever is done faster
* by your compiler. (Note that this type is only used in the floating point
* DCT routines, so it only matters if you've defined DCT_FLOAT_SUPPORTED.)
* Typically, float is faster in ANSI C compilers, while double is faster in
* pre-ANSI compilers (because they insist on converting to double anyway).
* The code below therefore chooses float if we have ANSI-style prototypes.
*/
#ifndef FAST_FLOAT
#ifdef HAVE_PROTOTYPES
#define FAST_FLOAT float
#else
#define FAST_FLOAT double
#endif
#endif
#endif /* JPEG_INTERNAL_OPTIONS */
3、修改项目的属性
(1)右键项目名，修改输出类型为 DLL
(2)在预处理器选项中，删除 _LIB 选项，新增 LIBJPEG_EXPORTS选项
4、编译工程
编译成功后，会在输出目录下生成dll 和lib 文件，这样我们就可以调用了。
