前言
本想写个从.wdf提前资源的生成位图的程序，无奈.bmp没有A(透明色),.gif编码复杂，所以选择.png作为理想的图片格式,饶了许多弯路，发出来与各位分享心得
PNG的文件结构
由文件头+各种各样的PNG数据块Chunk组成（其中最主要是的IHDR(图像描述信息，如宽度，高度，是否真彩色..),IDAT(图像数据),IEND(文件尾终止符)），顺序也这样
这是生成的1x1一个红色像素的PNG图片
Chunk
PNG数据块Chunk 由 数据块长度，数据块标识，数据内容,CRC校验码组成
如 IHDR CHunk 
| 名称 | 描述 |
|---|---|
| 文件头 | 0x89,0x50,0x4E,0x47,0x0D,0x0A,0x1A,0x0A （ASCII为’.PNG….’ 一共8个字节 生成文件时直接复制） |
| IHDR | 图像描述信息，如宽度，高度，是否真彩色.. |
| IDAT | 图像数据 |
| IEND | 文件尾终止符 |
各个字段解析如下 类型只选了最简单的
class Chunk
{
public:
DWORD ChunkLen;//ChunkLen 不算 ChunkLen，Tag，CRC的长度
DWORD Tag;//4byte
DWORD CRC;效验码
};class IHDR : public Chunk
{
public:
DWORD Width;//宽
DWORD Height;//高
BYTE BitDepth;//位深 真彩色图像：8或16
BYTE ColorType;//颜色类型 6：带α通道数据的真彩色图像，8或16
BYTE CompressionMethod;//压缩方法(LZ77派生算法) 固定0
BYTE FilterMethod;//滤波器方法 固定0
BYTE InterlaceMethod;//隔行扫描方法：0：非隔行扫描 1： Adam7(由Adam M.Costello开发的7遍隔行扫描方法)
}；class IDAT :public Chunk
{
public:
BYTE* CompressData;//zib压缩数据
DWORD CompressDataLen;//zib压缩数据长度(这个这是我个人加的，方便复制数据 文件结构里面没有这个)
}class IEND :public Chunk
{
//没有数据
}IDAT
IDAT 像素数据是顺序排列 （最左上角的像素点在buff最前面，最右下角的像素点在buff最尾端 ），每个像素(32位的图片)点由 红(8)绿(8)蓝(8)A(8)组合， 每行像素点开始需要多加一个0 如下面1x2的图片 
，整个像素数据是zib压缩（算法。。。）这个怎么用 我已经写在代码里了
生成png源码
#include <Windows.h>
#include <iostream>
#include <io.h>
#include "zlib.h"
#pragma warning( disable : 4996 )//忽略非安全函数
#pragma comment (lib,"zlib.lib")
#define png_IHDR 0x49484452
#define png_IDAT 0x49444154
#define png_IEND 0x49454e44
#define png_IEND_CRC 0xAE426082
const static BYTE png_Title[] = { 0x89,0x50,0x4E,0x47,0x0D,0x0A,0x1A,0x0A }; //.PNG....
DWORD ChgDWORD(DWORD value)
{
DWORD ret = 0;
auto pret = (BYTE*)&ret;
auto pvalue = (BYTE*)&value;
*pret++ = pvalue[3];
*pret++ = pvalue[2];
*pret++ = pvalue[1];
*pret++ = pvalue[0];
return ret;
}
WORD ChgWORD(WORD value)
{
__asm
{
mov ax, value
xchg al, ah
mov value, ax
}
return value;
}
//复制内容并且同时移动指针
inline void Xmemmove(BYTE* &buff, void * value, int size)
{
memmove(buff, value, size);
buff += size;
}
#pragma pack (push)
#pragma pack (1)
class Chunk
{
public:
DWORD ChunkLen;//ChunkLen 不算 ChunkLen，Tag，CRC的长度
DWORD Tag;//4byte
DWORD CRC;
};
class IHDR : public Chunk
{
public:
DWORD Width;//宽
DWORD Height;//高
BYTE BitDepth;//位深 真彩色图像：8或16
BYTE ColorType;//颜色类型 6：带α通道数据的真彩色图像，8或16
BYTE CompressionMethod;//压缩方法(LZ77派生算法) 固定0
BYTE FilterMethod;//滤波器方法 固定0
BYTE InterlaceMethod;//隔行扫描方法：0：非隔行扫描 1： Adam7(由Adam M.Costello开发的7遍隔行扫描方法)
public:
void WriteMemoryAndCRC(BYTE* &buff)
{
DWORD tempDWORD = 0;
Xmemmove(buff, &(tempDWORD = ChgDWORD(ChunkLen)), sizeof(ChunkLen));
auto buff_begin = buff;
Xmemmove(buff, &(tempDWORD = ChgDWORD(Tag)), sizeof(Tag));
Xmemmove(buff, &(tempDWORD = ChgDWORD(Width)), sizeof(Width));
Xmemmove(buff, &(tempDWORD = ChgDWORD(Height)), sizeof(Height));
Xmemmove(buff, &BitDepth, sizeof(BitDepth));
Xmemmove(buff, &ColorType, sizeof(ColorType));
Xmemmove(buff, &CompressionMethod, sizeof(CompressionMethod));
Xmemmove(buff, &FilterMethod, sizeof(FilterMethod));
Xmemmove(buff, &InterlaceMethod, sizeof(InterlaceMethod));
//CRC
CRC = crc32(0, buff_begin, buff - buff_begin);
Xmemmove(buff, &(tempDWORD = ChgDWORD(CRC)), sizeof(CRC));
}
};
class IDAT :public Chunk
{
public:
BYTE* CompressData;
DWORD CompressDataLen;
public:
void WriteMemoryAndCRC(BYTE* &buff)
{
DWORD tempDWORD = 0;
Xmemmove(buff, &(tempDWORD = ChgDWORD(ChunkLen)), sizeof(ChunkLen));
auto buff_begin = buff;
Xmemmove(buff, &(tempDWORD = ChgDWORD(Tag)), sizeof(Tag));
Xmemmove(buff, CompressData, CompressDataLen);
//CRC
CRC = crc32(0, buff_begin, buff - buff_begin);
Xmemmove(buff, &(tempDWORD = ChgDWORD(CRC)), sizeof(CRC));
};
};
class IEND :public Chunk
{
public:
void WriteMemoryAndCRC(BYTE* &buff)
{
DWORD tempDWORD = 0;
Xmemmove(buff, &(tempDWORD = ChgDWORD(ChunkLen)), sizeof(ChunkLen));
Xmemmove(buff, &(tempDWORD = ChgDWORD(Tag)), sizeof(Tag));
CRC = png_IEND_CRC;
Xmemmove(buff, &(tempDWORD = ChgDWORD(CRC)), sizeof(CRC));
}
};
#pragma pack (pop)
/*创建Png函数（已经格式化数据）
ImgData=>(红绿蓝A)(每行开始有个0)(第一行0RGBA BGRA BGRA....第二行0BGRA BGRA BGRA....)(A=0透明A=0xFF不透明)
PNGBuff=>函数内部创建
*/
void CreatePNGByFormatData(DWORD Witdh, DWORD Height, BYTE *ImgBuff, int ImgBuffLen, void *& PNGBuff, int & PNGBuffLen)
{
//head info
IHDR head;
head.ChunkLen = sizeof(IHDR) - sizeof(Chunk);
head.Tag = png_IHDR;
head.Width = Witdh;
head.Height = Height;
head.BitDepth = 8;
head.ColorType = 6;
head.CompressionMethod = 0;
head.FilterMethod = 0;
head.InterlaceMethod = 0;
//数据段
IDAT data;
data.Tag = png_IDAT;
auto compressLen = compressBound(ImgBuffLen);
data.CompressData = new BYTE[compressLen];
data.CompressDataLen = compressLen;
//此含树 第二个参数 需传入dest的长度 同时返回压缩后实际的数据长度
compress2(data.CompressData, &data.CompressDataLen, ImgBuff, ImgBuffLen, 0);
data.ChunkLen = sizeof(data.CRC) + sizeof(data.Tag) + data.CompressDataLen;
//IENDinfo
IEND end;
end.Tag = png_IEND;
//IEND长度为0
end.ChunkLen = 0;
//计算缓冲区大小
int buff_size = sizeof(png_Title) + sizeof(IHDR) + sizeof(IEND);
//加上IDAT(数据段)
buff_size += data.ChunkLen + sizeof(data.ChunkLen);
PNGBuffLen = buff_size;
//创建缓冲区
BYTE *buff = new BYTE[buff_size];
PNGBuff = buff;
//title
Xmemmove(buff, (void *)png_Title, sizeof(png_Title));
//head
head.WriteMemoryAndCRC(buff);
//data1
data.WriteMemoryAndCRC(buff);
//释放data1.CompressData
delete data.CompressData;
//end
end.WriteMemoryAndCRC(buff);
}
/*格式化函数*/
void PNGFormatData_R8G8B8A8(BYTE *& dest, int & desLen, BYTE * source, int sourceWitdh, int sourceHeight)
{
//png每行多一个字节0
desLen = sourceWitdh * sourceHeight * 4 + sourceHeight;
BYTE* buff = new BYTE[desLen];
dest = buff;
//源位图每行字节数量
int witdhSteps = sourceWitdh * 4;
for (size_t i = 0; i < sourceHeight; i++)
{
*buff++ = 0;
memcpy(buff, source, witdhSteps);
buff += witdhSteps;
source += witdhSteps;
}
}
void main()
{
//源图像
int imgWidth =512;
int imgHeight = 512;
BYTE *ImgData=new BYTE[imgWidth*imgHeight*4];
for (size_t i = 0,len= imgHeight*imgWidth; i < len; i++)
{
auto item = ImgData + int(i << 2);
item[0] = 0xff;//R
item[1] = 0x00;//G
item[2] = 0x00;//B
item[3] = 0xff;//A
}
{
auto item = ImgData + imgHeight*imgWidth*4-4;
item[0] = 0x00;//R
item[1] = 0xff;//G
item[2] = 0x00;//B
item[3] = 0xff;//A
}
//png图像
void * pngbuff = 0;
int buff_len = 0;
//pngIDATImg数据
BYTE * pngIDATbuff = 0;
int pngIDATbuffLen = 0;
//函数调用
PNGFormatData_R8G8B8A8(pngIDATbuff, pngIDATbuffLen, ImgData, imgWidth, imgHeight);
CreatePNGByFormatData(imgWidth, imgHeight, pngIDATbuff, pngIDATbuffLen, pngbuff, buff_len);
//资源释放
delete pngIDATbuff;
//文件操作
auto filename = "D:/Demo/myex/Beta/img/testcrc.png";
auto file = fopen(filename, "wb+");
fwrite(pngbuff, buff_len, 1, file);
fclose(file);
auto ret = 0;
/*
DWORD ImgData[] = { 0xff00ff00,0xff00ffff };
BYTE source[20];
ULONG sourceLen=20;
memset(source,0,sizeof(source));
compress2(source, &sourceLen, (Byte *)ImgData,8,0);
int ret = 0;*/
}