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POReading BMP in C++ strange behavior
 

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    <p>Thank you in advance!</p> <p>I'm reading a BMP in C++ using self-defined BITMAPFILEHEADER and BITMAPINFOHEADER. Then I print it out using SetPixel(). But there're some problems with the printing order of pixels and I failed to fix it. To illustrate them, please see the images provided. I don't have enough reputations to upload images here so please check the url. Sorry for the inconvenience:(</p> <p><a href="http://liuyuel.blogspot.com/2012/02/reading-bmp-in-c.html" rel="nofollow">http://liuyuel.blogspot.com/2012/02/reading-bmp-in-c.html</a></p> <p>Above two are 256*256 lena.bmp. The first one is the original one, and the second one is the result of my program. See the left-most out-of-order bar? It should appear in the right-most as in the original image.</p> <p>I also tried some random bmp files. But with this one I got a strange color.</p> <p>(Still see the above link) Its size is 146*146. The third image is the original and fourth is the printed result. I used a screen capturing tool to snip it from the internet, so I don't know if the problem is in my program (but it didn't exist in lena.bmp!) or is in the bmp itself.</p> <p>My code is as below:</p> <pre><code>/*****BMP.h*****/ #include &lt;fstream&gt; #include &lt;Windows.h&gt; #define N 384 using namespace std; typedef struct { WORD bfType; /* Magic identifier */ DWORD bfSize; /* File size in bytes */ WORD bfReserved1; WORD bfReserved2; DWORD bfOffBits; /* Offset to image data, bytes */ } HEADER; typedef struct { DWORD biSize; /* Header size in bytes */ LONG biWidth; /* Width and height of image */ LONG biHeight; WORD biPlanes; /* Number of colour planes */ WORD biBitCount; /* Bits per pixel */ DWORD biCompression; /* Compression type */ DWORD biSizeImage; /* Image size in bytes */ LONG biXPelsPerMeter; /* Pixels per meter */ LONG biYPelsPerMeter; DWORD biClrUsed; /* Number of colours */ DWORD biClrImportant; /* Important colours */ } INFOHEADER; /*****main.cpp*****/ #include "BMP.h" HEADER bmfh; //bitmap file header INFOHEADER bmih; //bitmap info header BYTE R[N][N], G[N][N], B[N][N]; //RGB value of every pixel COLORREF color[N][N]; //color extern "C" WINBASEAPI HWND WINAPI GetConsoleWindow (); //initialize the screen void ReadBmp(char *BmpFileName); void GetColor(int i, int j); void main() { HWND hwnd; //handlers HWND and HDC HDC hdc; char BmpFileName[10]; int i, j; hwnd = GetConsoleWindow(); //initialize the screen hdc = GetDC(hwnd); scanf("%s", BmpFileName); ReadBmp(BmpFileName); //read the BMP file for(i = 0; i &lt; bmih.biHeight; i++) for(j = 0; j &lt; bmih.biWidth; j++) SetPixel(hdc, i, j, color[bmih.biWidth - j][i]); //draw the BMP image ReleaseDC(hwnd,hdc); } void ReadBmp(char *BmpFileName) //read the BMP file { int patch; //number of 0s for complement in every row ifstream in(BmpFileName, ios_base::binary); //open the BMP file in.read((char *)(&amp;bmfh), sizeof(bmfh) - 2); //read in BITMAPFILEHEADER. Here sizeof returns a value larger than struct size, so "-2" if(bmfh.bfType != 0x4d42) //if not BMP, exit { printf("File type is not BMP!\n"); exit(1); } in.read((char *)(&amp;bmih),sizeof(bmih)); //read in BITMAPINFOHEADER in.seekg(bmfh.bfOffBits, ios_base::beg); //seek bitmap data patch = (4 - (bmih.biWidth * 3) % 4) % 4; //calculate number of 0s for complement in every row for(int i = 0; i &lt; abs(bmih.biHeight); i++) { for(int j = 0; j &lt; abs(bmih.biWidth); j++) { in.read((char *)(&amp;R[i][j]), 1); //read in data pixel by pixel in.read((char *)(&amp;G[i][j]), 1); in.read((char *)(&amp;B[i][j]), 1); GetColor(i, j); //obtain the original and greyscaled color } in.seekg(patch, ios_base::cur); //skip 0s for complement in every row } } void GetColor(int i, int j) //obtain the original and greyscaled color { int iB, iG, iR; iB = (int)(B[i][j]); iG = (int)(G[i][j]); iR = (int)(R[i][j]); color[i][j] = RGB(iB, iG, iR); //original color } </code></pre>
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    1. USgoldfrapp04
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    1. COThe `Windows.h` header file already provides [`BITMAPFILEHEADER`](http://msdn.microsoft.com/en-us/library/dd183374.aspx) and [`BITMAPINFOHEADER`](http://msdn.microsoft.com/en-us/library/dd183376.aspx). If you're including it, why are you redefining the structures?
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      1. POReading BMP in C++ strange behavior
      1. USAndré Caron
    2. COBTW: your lena image is also wrong, only that it's not that striking, because the colors are not affected. It *is* shifted to the right though, just like the other image.
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      1. POReading BMP in C++ strange behavior
      1. USPaul Groke
    3. CO@AndréCaron simply because in the homework we're required to do so...
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      1. USgoldfrapp04
 

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