How to open a BMP file with IPP?

[wwang]

I am new to IPP. Before I can do any image processing, I need to open the images that are stored in .bmp files. Is there a function in IPP that opens a .bmp file or do I need to do it outside the library and feed the resulting data matrix into IPP functions? Thanks.

[Vladimir_Dudnik]

Hello,

For such a basic questions you can find answers on that forum, for example:

Loading an image
Loading an Ippi image
Image processing
Need a simple way to read and display image files

Well, after review of those question I see that probably piece of simple code to read BMP file can help

#define DIB_ALIGN (sizeof(int) - 1)

#define DIB_UWIDTH(width,nchannels) 
 ((width) * (nchannels))

#define DIB_AWIDTH(width,nchannels) 
 ( ((DIB_UWIDTH(width,nchannels) + DIB_ALIGN) & (~DIB_ALIGN)) )

#define DIB_PAD_BYTES(width,nchannels) 
( DIB_AWIDTH(width,nchannels) - DIB_UWIDTH(width,nchannels) )

/* Open BMP file */

int read_bmp(
 char* fname,
 Ipp8u** bmBits,
 int* bmStep,
 IppiSize* bmSize,
 int* nchannels)
{
 int i, j;
 int res = 0;
 int pad;
 int step;
 int size;
 size_t cnt;
 Ipp8u* ptr;
 Ipp8u* buff = NULL;
 FILE * bmpf = NULL;
 BITMAPFILEHEADER bmfh;
 BITMAPINFOHEADER bmih;
 RGBQUAD palette[256];

 bmpf = fopen(fname,"rb");
 if(NULL == bmpf)
 {
 fprintf(stderr,"ERROR: can't open file %s
",fname);
 res = -1;
 goto Exit;
 }

 cnt = fread(&bmfh,sizeof(char),sizeof(BITMAPFILEHEADER),bmpf);
 if(cnt != sizeof(BITMAPFILEHEADER))
 {
 fprintf(stderr,"ERROR: can't read from file
");
 res = -1;
 goto Exit;
 }

 if(bmfh.bfType != 0x4d42)
 {
 fprintf(stderr,"ERROR: invalid file format
");
 res = -1;
 goto Exit;
 }

 cnt = fread(&bmih,sizeof(char),sizeof(BITMAPINFOHEADER),bmpf);
 if(cnt != sizeof(BITMAPINFOHEADER))
 {
 fprintf(stderr,"ERROR: can't read from file
");
 res = -1;
 goto Exit;
 }

 if(bmih.biBitCount != 8 && bmih.biBitCount != 24)
 {
 fprintf(stderr,"ERROR: sorry, unsupported format for this example
");
 res = -1;
 goto Exit;
 }

 if(bmih.biBitCount == 8)
 {
 cnt = fread(palette,sizeof(char),sizeof(palette),bmpf);
 if(cnt != sizeof(palette))
 {
 fprintf(stderr,"ERROR: can't read from file
");
 res = -1;
 goto Exit;
 }
 }

 res = fseek(bmpf,bmfh.bfOffBits,SEEK_SET);
 if(0 != res)
 {
 fprintf(stderr,"Error: can't seek in file
n");
 goto Exit;
 }

 pad = DIB_PAD_BYTES(bmih.biWidth,bmih.biBitCount >> 3);
 step = (bmih.biWidth * (bmih.biBitCount >> 3) + pad);
 size = step * abs(bmih.biHeight);

 buff = (Ipp8u*)ippMalloc(size);
 if(NULL == buff)
 {
 fprintf(stderr,"ERROR: can't allocate memory
");
 res = -1;
 goto Exit;
 }

 if(bmih.biHeight > 0)
 {
 ptr = buff + (bmih.biHeight-1)*step;
 }
 else
 {
 ptr = buff;
 }

 for(i = 0; i < abs(bmih.biHeight); i++)
 {
 cnt = fread(ptr,sizeof(char),step,bmpf);
 if(cnt != (size_t)step)
 {
 fprintf(stderr,"ERROR: can't read from file
");
 res = -1;
 goto Exit;
 }

 if(bmih.biHeight > 0)
 {
 ptr -= step;
 }
 else
 {
 ptr += step;
 }
 }

 if(bmih.biBitCount == 8)
 {
 for(i = 0; i < abs(bmih.biHeight); i++)
 {
 ptr = buff + i*step;
 for(j = 0; j < bmih.biWidth; j++)
 {
 // for Gray all palette entries is equivalent
 int pal_index = ptr;
 Ipp8u gray = palette[pal_index].rgbBlue;
 ptr = gray;
 }
 }
 }

 *bmBits = buff;
 bmSize->width = bmih.biWidth;
 bmSize->height = abs(bmih.biHeight);
 *bmStep = step;
 *nchannels = bmih.biBitCount >> 3;

Exit:

 if(NULL != bmpf)
 {
 fclose(bmpf);
 }

 if(res != 0)
 {
 if(NULL != buff)
 {
 ippFree(buff);
 }
 }

 return res;
} /* read_bmp() */

Regards,
Vladimir