原始位图数据到jpeg或png C ++

Question

I have bytearray where every three bytes describes 1 pixel (RGB). The task is to convert it to jpeg or png.

Actually, I am using Zint (open source lib for generating barcodes) that uses libpng to generate image file and save it to file system, but in Zintthe function png_plot() except generating image also save it on disk which is undesirable.

As result I think there two ways:
1. from bitmap bytearray to bmp -> jpeg / png (using some other lib)
2. writing hook or some similar to png_plot()

Can you give me some advices? Thank you.

Upd: for @peacemaker

FILE *f;

zint_symbol *my_symbol;

my_symbol = ZBarcode_Create();


ZBarcode_Encode_and_Buffer(my_symbol, (unsigned char *)argv[1], 0, 0);

f = fopen("bitmap.bmp", "w");

fwrite(my_symbol->bitmap, sizeof(*(my_symbol->bitmap)), my_symbol->bitmap_height * my_symbol->bitmap_width, f);

ZBarcode_Delete(my_symbol);

fclose(f);

Answer 1

In order to convert between image formats, the easiest way would be using the class CImage shared by MFC and ATL and defined in the header file atlimage.h.

CImage image; 
HRESULT res = image.Load("in.bmp");
image.Save("out.jpg");
image.Save("out.gif");
image.Save("out.png");
image.Save("out.tif");

---

If you have a RGB buffer and want to create a bitmap: just create and save a bitmap header into a file and add the RGB buffer to it.

To create the header you can use the BITMAPFILEHEADER , BITMAPINFOHEADER and RGBQUAD structures from GDI defined in the header WinGDI.h

Here is an example on how to fill the header data:

BITMAPINFOHEADER bmpInfoHdr;

bmpInfoHdr.biSize = sizeof(BITMAPINFOHEADER);
bmpInfoHdr.biHeight = nHeight;
bmpInfoHdr.biWidth =  nWidthPadded;
bmpInfoHdr.biPlanes = 1;
bmpInfoHdr.biBitCount = bitsPerPixel;           
bmpInfoHdr.biSizeImage = nHeight * nWidthPadded * nSPP; 
bmpInfoHdr.biCompression =  BI_RGB; 
bmpInfoHdr.biClrImportant = 0;  
bmpInfoHdr.biClrUsed = 0;
bmpInfoHdr.biXPelsPerMeter = 0;
bmpInfoHdr.biYPelsPerMeter = 0;
bmpFileHdr.bfType = BITMAP_FORMAT_BMP;
bmpFileHdr.bfSize =  (DWORD) (sizeof(BITMAPFILEHEADER) + bmpInfoHdr.biSize +
                      sizeof(RGBQUAD)*numColors + bmpInfoHdr.biSizeImage);
bmpFileHdr.bfReserved1 = 0;
bmpFileHdr.bfReserved2 = 0;
bmpFileHdr.bfOffBits = (DWORD) (sizeof(BITMAPFILEHEADER) + bmpInfoHdr.biSize + 
                        sizeof(RGBQUAD)*numColors);

Keep into account that the bitmaps are stored upside-down and that the width of the image must be aligned on a DWORD except for RLE-compressed bitmaps.(they must be multiple of 4 bytes, add a padding if necessary).

if ((nWidth%4) != 0)
    nPadding = ((nWidth/4) + 1) * 4;

When saving your buffer, add the needed padding to each row...

Summarizing, these are the needed steps to create a bitmap file from a rgb buffer:

//1. create bmp header 

//2. save header to file:
 write(file, &bmpFileHdr, sizeof(BITMAPFILEHEADER));
 write(file, &bmpInfoHdr, sizeof(BITMAPINFOHEADER));
 write(file, &colorTable, numColors * sizeof(RGBQUAD));

//3. add rgb buffer to file:
for(int h=0; h<nHeight; h++) {
   for(int w=0; w<nWidth; w++) {
      //3.a) add row to file
      //3.b) add padding for this row to file
   }
}

Answer 2

I used the CImage Class from ATL.

int width=0, height=0;
char * val = "9788994774480"; 
zint_symbol *my_symbol;
my_symbol = ZBarcode_Create();

//ZBarcode_Encode_and_Buffer(my_symbol,(unsigned char *) val, 0, 0);
ZBarcode_Encode(my_symbol, (unsigned char *) val, 0);
ZBarcode_Buffer(my_symbol, 0);

height = my_symbol->bitmap_height;
width = my_symbol->bitmap_width;
char * imgBits = my_symbol->bitmap;

CImage img;
img.Create(width, height, 24 /* bpp */, 0 /* No alpha channel */);

int nPixel = 0;
for(int row = 0; row < height; row++)
{
    for(int col = 0; col < width; col++)
    {
        BYTE r = (BYTE)imgBits[nPixel];
        BYTE g = (BYTE)imgBits[nPixel+1];
        BYTE b = (BYTE)imgBits[nPixel+2];
        img.SetPixel(col, row , RGB(r, g, b));

        nPixel += 3;
    }
}

img.Save("CImage.bmp", Gdiplus::ImageFormatBMP);

ZBarcode_Delete(my_symbol);

Answer 3

is there anyway to do this other than using SetPixel? I am experiencing major performance issues with SetPixel and need an alternative method... I have tried using CreateDIBSection to no avail. The barcode displays slanted and is unusable. here is my code for that:

void *bits = (unsigned char*)(my_symbol->bitmap);
HBITMAP hBitmap = CreateDIBSection(pDC->GetSafeHdc(), &info, DIB_RGB_COLORS, (void **)&pDestData, NULL, 0);
memcpy(pDestData, my_symbol->bitmap, info.bmiHeader.biSizeImage);
img.Attach(hBitmap);

Another option that produces the same result is this:

    BITMAPINFO info;
    BITMAPINFOHEADER BitmapInfoHeader;    
    BitmapInfoHeader.biSize = sizeof(BITMAPINFOHEADER);   
    BitmapInfoHeader.biWidth = my_symbol->bitmap_width;
    BitmapInfoHeader.biHeight = -(my_symbol->bitmap_height);
    BitmapInfoHeader.biPlanes = 1;   
    BitmapInfoHeader.biBitCount = 24;   
    BitmapInfoHeader.biCompression = BI_RGB;  
    BitmapInfoHeader.biSizeImage = 0;   
    BitmapInfoHeader.biXPelsPerMeter = 0;   
    BitmapInfoHeader.biYPelsPerMeter = 0;   
    BitmapInfoHeader.biClrUsed = 0;   
    BitmapInfoHeader.biClrImportant = 0;

    info.bmiHeader = BitmapInfoHeader;

    HBITMAP hbmp = CreateDIBitmap(dc, &BitmapInfoHeader, CBM_INIT, (LPVOID *)my_symbol->bitmap, (LPBITMAPINFO)&info, DIB_RGB_COLORS);
    img.Attach(hbmp);