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Finding the image dimensions of a file without reading it

Guys,

I am wanting to find the dimensions of a image quickly. Now I know that there is a BITMAPFILEHEADER structure which can allow me to read the portion of the bitmap I want to read to get the width and height of the image.

-----
CFile file;
// sBMPFileName is the BMP filename
if( !file.Open( sBMPFileName, CFile::modeRead) )
return ;

BITMAPFILEHEADER bmfHeader;

// Read file header
if (file.Read((LPSTR)&bmfHeader, sizeof(bmfHeader)) != sizeof(bmfHeader))
return ;

// File type should be 'BM'
if (bmfHeader.bfType != ((WORD) ('M' << 8) | 'B'))
return ;

BITMAPINFOHEADER bmiHeader;
if (file.Read((LPSTR)&bmiHeader, sizeof(bmiHeader)) != sizeof(bmiHeader))
return ;

int bmWidth = bmiHeader.biWidth;
int bmHeight = bmiHeader.biHeight;
------

I want to be able to do this for all images. I have potentially thousands of images and the system need to perform an add of an image size e.g. 6x4" print from the file. I want to make sure that the image is off sufficient quality to allow reasonable printing quality.

Is there something similar to this in mfc / gdi+ to do the same thing for all image types .... jpg, bmp, tiff, pcx.

regards,

Gordon.

ASKER CERTIFIED SOLUTION

AlexFM

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jeffreyg

ASKER

Does this FromFile not load the image into the Bitmap?

I am using that already, for images that I display on the screen (12 thumbnails). I do what you suggest already.

1. Find out how many images there are in the directory I am in, by using CFileFind.
2. Create a linked list of placeholders for all the files.
3. Load the first 12 images in with the Bitmap::FromFile() function.
4. Don't load any more images atm, what if the user wants only the first image in a list of 2000 images?
5. If the user wants to view the next 12 images repeat process 3.
6. If the user clicks the select all images for a 6x4 print, load all the images that fulfill this criteria.

Now if the user does step 6 without loading all the images I don't know the image dimension.

Ideally when create my liked list of placeholders in step 2 I want to get the header information of the each image only.

regards,

Gordon.

jeffreyg

ASKER

P.S. I want to load all image types esp. jpg, bmp, tiff, gif.

regards,

Gordon.

jeffreyg

ASKER

Thanx Alex,

Best method I could find. It'll have to do.

:))