相机产生的文件中有(jpg)有个EXIF 段用来记录拍摄时的一些参数,MFC的gdiplus,已经支持这些参数的读取,不用自己费劲琢磨原始文件了。对于图像显示所用的主要参数是相机的旋转角度,知道这个旋转角度就可以自动将照片显示为实际的方向。
下面是笔者根据需要整理的一个简易的exif读取的类:
// An highlighted block
#pragma once
#include "stdafx.h"
#include <windows.h>
#include <gdiplus.h>
#include <stdio.h>
#include <map>
using namespace Gdiplus;
class CExif
{
private:
std::map<PROPID, PropertyItem> PrptItemMap;
PropertyItem* pAllItems;
public:
CExif()
{
pAllItems = nullptr;
}
~CExif()
{
if (pAllItems != nullptr) {
free(pAllItems);
}
}
void setImage(CString imgfile) {
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
// Create an Image object based on a JPEG file.
//Image* image = new Image(L"I:\\DC_PIC\\2017\\104ND600\\DSC_6648.jpg");//0x004e0300
//G:\CPP\MyImageKit\MyImageKit\res
Image* image = new Image(imgfile);//0x004e0300
// Find out how many property items are in the image, and find out the
// required size of the buffer that will receive those property items.
UINT totalBufferSize;
UINT numProperties;
image->GetPropertySize(&totalBufferSize, &numProperties);
// Allocate the buffer that will receive the property items.
pAllItems = (PropertyItem*)malloc(totalBufferSize);
// Fill the buffer.
image->GetAllPropertyItems(totalBufferSize, numProperties, pAllItems);
// Print the id data member of each property item.
for (UINT j = 0; j < numProperties; ++j)
{
std::pair<PROPID, PropertyItem> exifPair(pAllItems[j].id, pAllItems[j]);
PrptItemMap.insert(exifPair);
}
delete image;
GdiplusShutdown(gdiplusToken);
}
//1#PropertyTagOrientation
int getRotateAngle() {
short *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter=PrptItemMap.find(PropertyTagOrientation);
p = (short*)(iter->second.value);
// 1:0, 8: 90,3,180,6:-90, counterclock is +
int val;
int degree = 0;
val = p[0];
switch (val)
{
case 8:
degree = 90;
break;
case 3:
degree = 180;
break;
case 6:
degree = 270;
break;
default:
break;
}
return degree;
}
//2#PropertyTagEquipMake
int getEquipMake(char * retVal,int len ) {
char *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagEquipMake);
p = (char*)(iter->second.value);
strcpy_s(retVal, strlen(p) + 1,p);
return strlen(p)+1;
}
//3#PropertyTagEquipModel
int getEquipModel(char * retVal, int len) {
char *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagEquipModel);
p = (char*)(iter->second.value);
strcpy_s(retVal, strlen(p) + 1, p);
return strlen(p)+1;
}
//4#PropertyTagArtist
int getArtist(char * retVal, int len) {
char *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagArtist);
p = (char*)(iter->second.value);
strcpy_s(retVal, strlen(p)+1, p);
return strlen(p)+1;
}
//5#PropertyTagHostComputer
int getHostComputer(char * retVal, int len) {
char *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagHostComputer);
if (iter == PrptItemMap.end()) {
return 0;
}
p = (char*)(iter->second.value);
strcpy_s(retVal, strlen(p) + 1, p);
return strlen(p) + 1;
}
//5#PropertyTagExifExposureTime
int getExposureTime(long * retVal) {
long *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagExifExposureTime);
if (iter == PrptItemMap.end()) {
return 0;
}
p = (long*)(iter->second.value);
retVal[0] = p[0];
retVal[1] = p[1];
return iter->second.length;
}
//6#PropertyTagExifISOSpeed
int getISOSpeed() {
short *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagExifISOSpeed);
if (iter == PrptItemMap.end()) {
return 0;
}
p = (short*)(iter->second.value);
return *p;
}
//7#PropertyTagExifShutterSpeed
int getShutterSpeed() {
short *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagExifShutterSpeed);
if (iter == PrptItemMap.end()) {
return 0;
}
p = (short*)(iter->second.value);
return *p;
}
//8#PropertyTagExifAperture
int getAperture(char * retVal, int len) {
char *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagExifAperture);
if (iter == PrptItemMap.end()) {
return 0;
}
p = (char*)(iter->second.value);
strcpy_s(retVal, strlen(p) + 1, p);
return strlen(p) + 1;
}
//9#PropertyTagExifFocalLength
int getFocalLength(long * retVal) {
long *p;
std::map<PROPID, PropertyItem>::iterator iter;
iter = PrptItemMap.find(PropertyTagExifFocalLength);
if (iter == PrptItemMap.end()) {
return 0;
}
p = (long*)(iter->second.value);
retVal[0] = p[0];
retVal[1] = p[1];
return iter->second.length;
}
};
都已经经过测试,各位如果要求不高,可以拿去使用。
说明:获得的参数只是非常基本的参数,GPS数据没有读取。如果哪位有这方面的需求,可以留言。
2020/03/24 于泛五道口地区