bool GetJpgWidthHeight(wxChar* buf,int size,int&Width,int& Height)
{
bool ret=false;
#define M_SOF0 0xC0 /* Start Of Frame N */
#define M_SOF1 0xC1 /* N indicates which compression process */
#define M_SOF2 0xC2 /* Only SOF0-SOF2 are now in common use */
#define M_SOF3 0xC3
#define M_SOF5 0xC5 /* NB: codes C4 and CC are NOT SOF markers */
#define M_SOF6 0xC6
#define M_SOF7 0xC7
#define M_SOF9 0xC9
#define M_SOF10 0xCA
#define M_SOF11 0xCB
#define M_SOF13 0xCD
#define M_SOF14 0xCE
#define M_SOF15 0xCF
#define M_SOI 0xD8 /* Start Of Image (beginning of datastream) */
#define M_EOI 0xD9 /* End Of Image (end of datastream) */
#define M_SOS 0xDA /* Start Of Scan (begins compressed data) */
#define M_APP0 0xE0 /* Application-specific marker, type N */
#define M_APP12 0xEC /* (we don't bother to list all 16 APPn's) */
#define M_COM 0xFE /* COMment */
int marker;
int Index=0;
int c1, c2;
c1 = (BYTE)buf[Index++];
c2 = (BYTE)buf[Index++];
if (c1 != 0xFF || c2 != M_SOI)
return false;
else
{
marker = c2;
}
unsigned int SkipLen=0;
for (;;)
{
marker=(BYTE)buf[Index++];
if(Index>=size)
return false;
while (marker != 0xFF)
{
marker=(BYTE)buf[Index++];
if(Index>=size)
return false;
}
do
{
marker=(BYTE)buf[Index++];
if(Index>=size)
return false;
} while (marker == 0xFF);
switch (marker)
{
case M_SOF0: /* Baseline */
case M_SOF1: /* Extended sequential, Huffman */
case M_SOF2: /* Progressive, Huffman */
case M_SOF3: /* Lossless, Huffman */
case M_SOF5: /* Differential sequential, Huffman */
case M_SOF6: /* Differential progressive, Huffman */
case M_SOF7: /* Differential lossless, Huffman */
case M_SOF9: /* Extended sequential, arithmetic */
case M_SOF10: /* Progressive, arithmetic */
case M_SOF11: /* Lossless, arithmetic */
case M_SOF13: /* Differential sequential, arithmetic */
case M_SOF14: /* Differential progressive, arithmetic */
case M_SOF15: /* Differential lossless, arithmetic */
Index+=3;
if(Index>=size)
return false;
c1=(BYTE)buf[Index++];
c2=(BYTE)buf[Index++];
Width=(int)(((unsigned int) c1) << 8) + ((unsigned int) c2);
c1=(BYTE)buf[Index++];
c2=(BYTE)buf[Index++];
Height=(int)(((unsigned int) c1) << 8) + ((unsigned int) c2);
return true;
break;
case M_SOS: /* stop before hitting compressed data */
return false;
break;
case M_EOI: /* in case it's a tables-only JPEG stream */
return false;
break;
default:
c1=(BYTE)buf[Index++];
c2=(BYTE)buf[Index++];
SkipLen=(((unsigned int) c1) << 8) + ((unsigned int) c2);
if (SkipLen < 2)
return false;
Index+=SkipLen-2;
if(Index>=size)
return false;
break;
}
}
return ret;
}
以上有些地方沒有偵測是否超過範圍，也不知道是不是通用所有的JPEG格式，所以使用以上程式發生問題本人概不負責 XD
另外傳入的buffer 要夠大 才會顯示真的長寬，有的圖檔的Width Height 位置非常的後面，並不是固定的位置
歡迎轉載，但請標明出處，謝謝。
參考網址： Google CodeSearch
