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Visualizza la versione completa : Problemi a caricare immagine bmp 24 bit in C


aissela84
06-08-2010, 12:58
Ciao a tutti, devo caricare una immagine bmp a 24 bit in C na ho dei problemi. Ho trovato questa funzione che però funziona per i file bmp 24 bit. Quindi dovrei aggiustare offset e altri valori. Il codice è il segunte:


//La funzione create_allocate_bmp_file setta l'altezza e la larghezza dell'immagine bmp.

create_allocate_bmp_file(file_name, file_header, bmheader)
char *file_name;
struct bmpfileheader *file_header;
struct bitmapheader *bmheader;
{
char buffer[100];
int i, pad = 0;
FILE *fp;
pad = calculate_pad(bmheader->width);
bmheader->size = 40; //questo dovrebbe rimanere invariato con 24 bit bmheader->planes = 1;
bmheader->bitsperpixel = 8; //ovviamento questo 24
bmheader->compression = 0;
bmheader->sizeofbitmap = bmheader->height * (bmheader->width + pad); //questo rimane invariato???
bmheader->horzres = 300;
bmheader->vertres = 300;
bmheader->colorsused = 256; //dovrebbe rimanere invariato
bmheader->colorsimp = 256; //dovrebbe rimanere invariato
file_header->filetype = 0x4D42;
file_header->reserved1 = 0;
file_header->reserved2 = 0;
file_header->bitmapoffset = 14 + bmheader->size + bmheader->colorsused*4; //l'offset cambia?????
file_header->filesize = file_header->bitmapoffset + bmheader-> sizeofbitmaps
if((fp = fopen(file_name, "wb")) == NULL){
printf("\nERROR Non è possibile creare il file %s", file_name);
exit(2); }
//Scrive i primi 14 bytes del file header bmp.
insert_ushort_into_buffer(buffer, 0, file_header->filetype);
fwrite(buffer, 1, 2, fp); //signature, must be 4D42 hex.

insert_ulong_into_buffer(buffer, 0, file_header->filesize);
fwrite(buffer, 1, 4, fp); //size of BMP file in bytes.

insert_short_into_buffer(buffer, 0, file_header->reserved1);
fwrite(buffer, 1, 2, fp); //reserved, must be 0.

insert_short_into_buffer(buffer, 0, file_header->reserved2);
fwrite(buffer, 1, 2, fp); //reserved, must be 0.

insert_ulong_into_buffer(buffer, 0, file_header->bitmapoffset);
fwrite(buffer, 1, 4, fp); //offset to start of image data in bytes.

// Scrive i successivi 40 bytes del bitmap header.

insert_ulong_into_buffer(buffer, 0, bmheader->size);
fwrite(buffer, 1, 4, fp); //sizeof bitmap header structure, must be 40.

insert_long_into_buffer(buffer, 0, bmheader->width);
fwrite(buffer, 1, 4, fp); //image width in pixels.

insert_long_into_buffer(buffer, 0, bmheader->height);
fwrite(buffer, 1, 4, fp); //image height in pixels.

insert_ushort_into_buffer(buffer, 0, bmheader->planes);
fwrite(buffer, 1, 2, fp); //number of planes in the image, must be 1.

insert_ushort_into_buffer(buffer, 0, bmheader->bitsperpixel);
fwrite(buffer, 1, 2, fp); //number of bits per pixel, must be 24.

insert_ulong_into_buffer(buffer, 0, bmheader->compression);
fwrite(buffer, 1, 4, fp); //compression type.

insert_ulong_into_buffer(buffer, 0, bmheader->sizeofbitmap);
fwrite(buffer, 1, 4, fp); //size of image data in bytes (including padding).

insert_ulong_into_buffer(buffer, 0, bmheader->horzres);
fwrite(buffer, 1, 4, fp); //horizontal resoltuion in pixels per meter (unreliable).

insert_ulong_into_buffer(buffer, 0, bmheader->vertres);
fwrite(buffer, 1, 4, fp); //vertical resoltion in pixels per meter (unreliable).

insert_ulong_into_buffer(buffer, 0, bmheader->colorsused);
fwrite(buffer, 1, 4, fp);// number of colors in image, or zero.

insert_ulong_into_buffer(buffer, 0, bmheader->colorsimp);
fwrite(buffer, 1, 4, fp); //number of important colors, or zero.

//Scrive una tabella dei colori bianca. Ha 256 entrate (numero di colori) che sono ognuno 4

bytes buffer[0] = 0x00;
for(i=0; i<(256*4); i++)
fwrite(buffer, 1, 1, fp);
//Scrive una immagine vuota.
buffer[0] = 0x00;
for(i=0; i<bmheader->sizeofbitmap; i++)
fwrite(buffer, 1, 1, fp);
fclose(fp); }

E' da più di una settimana che vado avanti e ormai non so più dove sbattare la testa. Qualcuno sa dirmi dove sbaglio? Quando salvo l'immagine poi mi si salva un'immagine danneggiata che non si riesce ad aprire. RIngrazio in anticipo.

linoma
06-08-2010, 13:18
Prova se riesci con questo (http://www.dreamincode.net/code/snippet849.htm)

oppure questo direttamente da MSDN.




Many applications store images permanently as files. For example, drawing applications store pictures, spreadsheet applications store charts, CAD applications store drawings, and so on.

If you are writing an application that will store a bitmapped image in a file, you should use the Windows file format described in Bitmap Storage. In order to store a bitmap in this format, you must initialize a BITMAPINFO structure (consisting of a BITMAPFILEHEADER structure and an array of RGBQUAD structures), as well as an array of palette indices.
The following example code defines a function that allocates memory for and initializes members within a BITMAPINFOHEADER structure.

PBITMAPINFO CreateBitmapInfoStruct(HWND hwnd, HBITMAP hBmp) {
BITMAP bmp;
PBITMAPINFO pbmi;
WORD cClrBits;

/* Retrieve the bitmap's color format, width, and height. */

if (!GetObject(hBmp, sizeof(BITMAP), (LPSTR)&bmp))
errhandler("GetObject", hwnd);


/* Convert the color format to a count of bits. */

cClrBits = (WORD)(bmp.bmPlanes * bmp.bmBitsPixel);

if (cClrBits == 1)
cClrBits = 1;

else if (cClrBits <= 4)
cClrBits = 4;
else if (cClrBits <= 8)
cClrBits = 8;
else if (cClrBits <= 16)
cClrBits = 16;
else if (cClrBits <= 24)
cClrBits = 24;
else
cClrBits = 32;

/*
* Allocate memory for the BITMAPINFO structure. (This structure
* contains a BITMAPINFOHEADER structure and an array of RGBQUAD data
* structures.)
*/

if (cClrBits != 24)
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,

sizeof(BITMAPINFOHEADER) +
sizeof(RGBQUAD) * (2^cClrBits));

/*
* There is no RGBQUAD array for the 24-bit-per-pixel format.
*/

else
pbmi = (PBITMAPINFO) LocalAlloc(LPTR,
sizeof(BITMAPINFOHEADER));



/* Initialize the fields in the BITMAPINFO structure. */

pbmi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
pbmi->bmiHeader.biWidth = bmp.bmWidth;

pbmi->bmiHeader.biHeight = bmp.bmHeight;
pbmi->bmiHeader.biPlanes = bmp.bmPlanes;
pbmi->bmiHeader.biBitCount = bmp.bmBitsPixel;
if (cClrBits < 24)
pbmi->bmiHeader.biClrUsed = 2^cClrBits;


/* If the bitmap is not compressed, set the BI_RGB flag. */

pbmi->bmiHeader.biCompression = BI_RGB;

/*
* Compute the number of bytes in the array of color
* indices and store the result in biSizeImage.
*/


pbmi->bmiHeader.biSizeImage = (pbmi->bmiHeader.biWidth + 7) /8
* pbmi->bmiHeader.biHeight
* cClrBits;

/*
* Set biClrImportant to 0, indicating that all of the
* device colors are important.
*/

pbmi->bmiHeader.biClrImportant = 0;

return pbmi;

}


The following example code defines a function that initializes the remaining structures, retrieves the array of palette indices, opens the file, copies the data, and closes the file.

void CreateBMPFile(HWND hwnd, LPTSTR pszFile, PBITMAPINFO pbi,
HBITMAP hBMP, HDC hDC)
{

HANDLE hf; /* file handle */
BITMAPFILEHEADER hdr; /* bitmap file-header */
PBITMAPINFOHEADER pbih; /* bitmap info-header */
LPBYTE lpBits; /* memory pointer */
DWORD dwTotal; /* total count of bytes */
DWORD cb; /* incremental count of bytes */
BYTE *hp; /* byte pointer */

DWORD dwTmp;


pbih = (PBITMAPINFOHEADER) pbi;
lpBits = (LPBYTE) GlobalAlloc(GMEM_FIXED, pbih->biSizeImage);
if (!lpBits)
errhandler("GlobalAlloc", hwnd);

/*
* Retrieve the color table (RGBQUAD array) and the bits
* (array of palette indices) from the DIB.
*/

if (!GetDIBits(hDC, hBMP, 0, (WORD) pbih->biHeight,
lpBits, pbi, DIB_RGB_COLORS))
errhandler("GetDIBits", hwnd);


/* Create the .BMP file. */

hf = CreateFile(pszFile,
GENERIC_READ | GENERIC_WRITE,
(DWORD) 0,
(LPSECURITY_ATTRIBUTES) NULL,
CREATE_ALWAYS,
FILE_ATTRIBUTE_NORMAL,
(HANDLE) NULL);

if (hf == INVALID_HANDLE_VALUE)
errhandler("CreateFile", hwnd);

hdr.bfType = 0x4d42; /* 0x42 = "B" 0x4d = "M" */

/* Compute the size of the entire file. */


hdr.bfSize = (DWORD) (sizeof(BITMAPFILEHEADER) +
pbih->biSize + pbih->biClrUsed
* sizeof(RGBQUAD) + pbih->biSizeImage);

hdr.bfReserved1 = 0;
hdr.bfReserved2 = 0;

/* Compute the offset to the array of color indices. */

hdr.bfOffBits = (DWORD) sizeof(BITMAPFILEHEADER) +
pbih->biSize + pbih->biClrUsed
* sizeof (RGBQUAD);

/* Copy the BITMAPFILEHEADER into the .BMP file. */


if (!WriteFile(hf, (LPVOID) &hdr, sizeof(BITMAPFILEHEADER),
(LPDWORD) &dwTmp, (LPOVERLAPPED) NULL))
errhandler("WriteFile", hwnd);

/* Copy the BITMAPINFOHEADER and RGBQUAD array into the file. */

if (!WriteFile(hf, (LPVOID) pbih, sizeof(BITMAPINFOHEADER)
+ pbih->biClrUsed * sizeof (RGBQUAD),
(LPDWORD) &dwTmp, (LPOVERLAPPED) NULL))
errhandler("WriteFile", hwnd);

/* Copy the array of color indices into the .BMP file. */


dwTotal = cb = pbih->biSizeImage;
hp = lpBits;
while (cb > MAXWRITE) {
if (!WriteFile(hf, (LPSTR) hp, (int) MAXWRITE,
(LPDWORD) &dwTmp, (LPOVERLAPPED) NULL))
errhandler("WriteFile", hwnd);
cb-= MAXWRITE;
hp += MAXWRITE;
}
if (!WriteFile(hf, (LPSTR) hp, (int) cb,
(LPDWORD) &dwTmp, (LPOVERLAPPED) NULL))
errhandler("WriteFile", hwnd);


/* Close the .BMP file. */

if (!CloseHandle(hf))
errhandler("CloseHandle", hwnd);

/* Free memory. */

GlobalFree((HGLOBAL)lpBits);
}

aissela84
06-08-2010, 14:47
il mio problema è capire se file_header->bitmapoffset devo metterlo a 54 e se si cosa devo mettere sulla size del bitmap?? per le bitmap 8 bit è bmheader->height* (bmheader->width + padding) ma con i 24 bit?

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