In depth knowledge of Meta-Structures and variables

[sabyasachi07]

[chandrakant100]

Good job @sabyasachi07 it will be really helpful for us while writing code in main.cpp

[H1manshu21]

Actual calculation for bfOffBits of BITMAPFILEHEADER,

bfOffBits = sizeof (BITMAPFILEHEADER) + NumberOfRGBTRIPLE * sizeof (RGBTRIPLE)  + sizeof (BITMAPINFOHEADER);

So looking into our 24bit image, it looks like this:

bfOffBits = 14 + 0 * 4  + 40;
// Prints 54
std::cout << bfOffBits;

• RGBTRIPLE variable is a color table. It is commonly either 16 colors or 256 colors, depending on how the file is specified in BITMAPINFOHEADER’s biBitCount.

• In our case, it does not exist in the file because we are using a 24-bit bitmap which is 2^24 = 16777216 colors and doesn't fit in RGBTRIPLE and the bmiColors member of BITMAPINFO is NULL.

• Each 3-byte triplet in the bitmap array represents the relative intensities of blue, green, and red, respectively, for a pixel. The bmiColors color table is used for optimizing colors used on palette-based devices, and must contain the number of entries specified by the biClrUsed member of the BITMAPINFOHEADER.

SOURCE: https://chowdera.com/2022/04/202204170049352833.html

[chandrakant100]

@Himanshu40 should we worry about the internal calculation because it is given by Microsoft

What about this?

bfOffBits = sizeof (BITMAPFILEHEADER) + NumberOfRGBTRIPLE * sizeof (RGBTRIPLE)  + sizeof (BITMAPINFOHEADER);

Have you tested it through std::cout @Himanshu40 ?

[H1manshu21]

@Himanshu40 should we worry about the internal calculation because it is given by Microsoft

What about this?

bfOffBits = sizeof (BITMAPFILEHEADER) + NumberOfRGBTRIPLE * sizeof (RGBTRIPLE)  + sizeof (BITMAPINFOHEADER);

Have you tested it through std::cout @Himanshu40 ?

Check: https://chowdera.com/2022/04/202204170049352833.html

[chandrakant100]

The calculation looks fine!

[H1manshu21]

The calculation looks fine!

Since in bmp.h there are three classes and they are being calculated as one I think? RGBTRIPLE structure describes a color consisting of relative intensities of red, green, and blue.

[sabyasachi07]

https://topic.alibabacloud.com/a/bitmapinfoheader-and-bitmapfileheader_8_8_32023995.html