本文主要是介绍centos7 C++ 调用libpng png转bmp，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
宽度不为4的倍数的png自动转为4的倍数的png，即扩展bmp的像素了。支持3通道（RGB）的png图片以及4通道(RGBA)的png图片解析。
下载地址：https://download.csdn.net/download/sz76211822/10800747
#ifndef __PARSE_PNG__
#define __PARSE_PNG__class ParsePng
{
public:ParsePng();~ParsePng();bool Parse(const char *pstrFilePath, unsigned char* pBitmapBuffer, long nBufferSize, long& nWidth, long& nHeight);private:void write_bmp_header(long nWidth, long nHeight, long nDepth);private:long m_nLenHeader;unsigned char* m_pImage;unsigned char* m_pCache;
};#endif
源文件:
#include "ParsePng.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>extern "C"{#include "include/png.h"
}#define MAX_LINE_SIZE 2 * 1024 * 1024
#define MAX_IMAGE_SIZE 20 * 1024 * 1024#pragma pack(2)
typedef struct BITMAPFILEHEADER {u_int16_t bfType;u_int32_t bfSize;u_int16_t bfReserved1;u_int16_t bfReserved2;u_int32_t bfOffBits;
} BITMAPFILEHEADER;typedef struct BITMAPINFOHEADER {u_int32_t biSize;u_int32_t biWidth;u_int32_t biHeight;u_int16_t biPlanes;u_int16_t biBitCount;u_int32_t biCompression;u_int32_t biSizeImage;u_int32_t biXPelsPerMeter;u_int32_t biYPelsPerMeter;u_int32_t biClrUsed;u_int32_t biClrImportant;
} BITMAPINFODEADER;ParsePng::ParsePng()
{m_nLenHeader = 0;m_pImage = NULL;while(!m_pImage){try{m_pImage = new unsigned char[MAX_IMAGE_SIZE];}catch(...){}}m_pCache = NULL;while(!m_pCache){try{m_pCache = new unsigned char[MAX_LINE_SIZE];}catch(...){}}
}
ParsePng::~ParsePng()
{if(m_pImage){delete[] m_pImage;m_pImage = NULL;}if(m_pCache){delete[] m_pCache;m_pCache = NULL;}
}
void ParsePng::write_bmp_header(long nWidth, long nHeight, long nDepth)
{struct BITMAPFILEHEADER bfh;struct BITMAPINFOHEADER bih;unsigned long headersize = 0;unsigned long filesize = 0;if(nWidth % 4 != 0){//4字节对齐nWidth += 4 - nWidth % 4;}if (nDepth == 1) {headersize = 14 + 40 + 256 * 4;filesize = headersize + nWidth * nHeight;}if (nDepth == 3) {headersize = 14 + 40;filesize = headersize + nWidth * nHeight * nDepth;}memset(&bfh, 0, sizeof(struct BITMAPFILEHEADER));memset(&bih, 0, sizeof(struct BITMAPINFOHEADER));//写入比较关键的几个bmp头参数bfh.bfType = 0x4D42;bfh.bfSize = filesize;bfh.bfOffBits = headersize;bih.biSize = 40;bih.biWidth = nWidth;bih.biHeight = nHeight;bih.biPlanes = 1;bih.biBitCount = (unsigned short)nDepth * 8;bih.biSizeImage = nWidth * nHeight * nDepth;memcpy(m_pImage, &bfh, sizeof(struct BITMAPFILEHEADER));memcpy(m_pImage + sizeof(struct BITMAPFILEHEADER), &bih, sizeof(struct BITMAPINFOHEADER));if (nDepth == 1) {//灰度图像要添加调色板unsigned char *platte = NULL;while(!platte){try{platte = new unsigned char[256*4];}catch(...){}}unsigned char j = 0;for (int i = 0; i < 1024; i += 4) {platte[i] = j;platte[i+1] = j;platte[i+2] = j;platte[i+3] = 0;j++;}memcpy(m_pImage + sizeof(struct BITMAPFILEHEADER) + sizeof(struct BITMAPINFOHEADER), platte, sizeof(unsigned char) * 1024);m_nLenHeader = sizeof(struct BITMAPFILEHEADER) + sizeof(struct BITMAPINFOHEADER) + sizeof(unsigned char) * 1024;delete[] platte;}else{m_nLenHeader = sizeof(struct BITMAPFILEHEADER) + sizeof(struct BITMAPINFOHEADER);}
}bool ParsePng::Parse(const char *pstrFilePath, unsigned char* pBitmapBuffer, long nBufferSize, long& nWidth, long& nHeight)
{m_nLenHeader = 0;memset(m_pImage, 0, MAX_IMAGE_SIZE);memset(m_pCache, 0, MAX_LINE_SIZE);FILE *pFile = fopen(pstrFilePath, "rb+");if(pFile){//文件打开失败png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);if (png_ptr == NULL){fclose(pFile);return false;}png_infop info_ptr = png_create_info_struct(png_ptr);if (info_ptr == NULL){fclose(pFile);png_destroy_write_struct(&png_ptr, NULL);return false;}if (setjmp(png_jmpbuf(png_ptr))){//如果程序跑到这里了，那么写入文件时出现了问题fclose(pFile);png_destroy_write_struct(&png_ptr, &info_ptr);return false;}rewind(pFile);png_init_io(png_ptr, pFile);//开始读文件png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_EXPAND, 0);//读文件/*获取宽度，高度，位深，颜色类型*/long nChannel = png_get_channels(png_ptr, info_ptr); //获取通道数long nDepth = png_get_bit_depth(png_ptr, info_ptr); //获取位深int color_type = png_get_color_type(png_ptr, info_ptr); //颜色类型/* row_pointers里边就是rgba数据 */png_bytep* row_pointers = png_get_rows(png_ptr, info_ptr);nWidth = png_get_image_width(png_ptr, info_ptr);nHeight = png_get_image_height(png_ptr, info_ptr);long nRemain = 0;if(nWidth % 4 != 0){nRemain = 4 - nWidth % 4;}write_bmp_header(nWidth, nHeight, 3);if(nChannel == 4 || color_type == PNG_COLOR_TYPE_RGB_ALPHA){/*如果是RGB+alpha通道，或者RGB+其它字节*/for(int i = nHeight - 1; i >= 0; i--){long nOffset = 0;for(int j = 0; j < nWidth * nChannel; j += nChannel){/* 一个字节一个字节的赋值 */m_pCache[nOffset++] = row_pointers[i][j + 2]; // redm_pCache[nOffset++] = row_pointers[i][j + 1]; // greenm_pCache[nOffset++] = row_pointers[i][j + 0]; // blue//m_pCache[j * 4 + 3] = row_pointers[i][j * 4 + 3]; // alpha}for(int i = 0; i < nRemain * 3; i++){//4字节对齐，比如图片宽度是157，那么补到160个像素。bmp每个像素占3个字节，故(160 - 157) * 3 = 9。我这里是补字节数m_pCache[nOffset++] = 0x00;}memcpy(m_pImage + m_nLenHeader, m_pCache, nOffset);m_nLenHeader += sizeof(unsigned char) * nOffset;}fclose(pFile);png_destroy_read_struct(&png_ptr, &info_ptr, 0);//撤销数据占用的内存if(pBitmapBuffer){if(nBufferSize >= m_nLenHeader){memcpy(pBitmapBuffer, m_pImage, m_nLenHeader);}}return true;}else if(nChannel == 3 || color_type == PNG_COLOR_TYPE_RGB){/* 如果是RGB通道 */for(int i = nHeight - 1; i >= 0; i--){long nOffset = 0;for(int j = 0; j < nChannel * nWidth; j += nChannel){/* 一个字节一个字节的赋值 */m_pCache[nOffset++] = row_pointers[i][j + 2]; // redm_pCache[nOffset++] = row_pointers[i][j + 1]; // greenm_pCache[nOffset++] = row_pointers[i][j + 0]; // blue}for(int i = 0; i < nRemain * 3; i++){//4字节对齐，比如图片宽度是157，那么补到160个像素。bmp每个像素占3个字节，故(160 - 157) * 3 = 9。我这里是补字节数m_pCache[nOffset++] = 0x00;}memcpy(m_pImage + m_nLenHeader, m_pCache, nOffset);m_nLenHeader += sizeof(unsigned char) * nOffset;}fclose(pFile);png_destroy_read_struct(&png_ptr, &info_ptr, 0);//撤销数据占用的内存if(pBitmapBuffer){if(nBufferSize >= m_nLenHeader){memcpy(pBitmapBuffer, m_pImage, m_nLenHeader);}}return true;}}return false;
}
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