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我仍然是C++的noob，我目前正在嘗試創建一個程序，它將256色位圖手動加載到數組中，並打印出每個像素的值CONSOL。看來這些價值觀，大多數時候，是不正確的。當從24位位圖讀取像素時出現奇怪的值
我的其他輸出（例如信息頭內的值）都很好，除了biSizeImage，它是5字節。這不應該是25字節嗎？
出於測試目的，我拍了兩張5 x 5的圖像。其中一個是全黑的，另一個是全白的。
我希望爲黑色，類似這樣的輸出：
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
0 0 0 0 0
但我得到：
0 0 0 0 0
0 0 0 0 0
3452816845 3452816845 3452816845 3452816845 3452816845
3452816845 3452816845 3452816845 3452816845 3452816845
3452816845 3452816845 3452816845 3452816845 3452816845
隨着全白畫面我的結果是更奇怪：
4294967295 255 4294967295 255 4294967295
255 4294967295 255 4294967295 255
3452816845 3452816845 3452816845 3452816845 3452816845
3452816845 3452816845 3452816845 3452816845 3452816845
3452816845 3452816845 3452816845 3452816845 3452816845
下面你可以看到我現在的代碼：
#include "stdafx.h"
#include <iostream>
#include <conio.h>
#include <string>
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
using namespace std;
#pragma pack(push,1)
typedef struct tagBITMAPFILEHEADER {
unsigned short bfType; // Specifies the type of file. This member must be BM. (0x4D42)
unsigned int bfSize; // Specifies the size of the file, in bytes.
short bfReserved1; // Reserved; must be set to zero.
short bfReserved2; // Reserved; must be set to zero.
unsigned int bfOffBits; // Specifies the byte offset from the BITMAPFILEHEADER structure to the actual bitmap data in the file.
} BITMAPFILEHEADER;
typedef struct tagBITMAPINFOHEADER {
unsigned int biSize; // Specifies the number of bytes required by the BITMAPINFOHEADER structure.
int biWidth; // Specifies the width of the bitmap, in pixels.
int biHeight; // Specifies the height of the bitmap, in pixels.
unsigned short biPlanes; // Specifies the number of planes for the target device. This member must be set to 1.
unsigned short biBitCount; // Specifies the number of bits per pixel. This value must be 1,4, 8, or 24.
unsigned int biCompression; // Specifies the type of compression for a compressed bitmap. Itcan be one of the following values: BI_RGB, BI_RLE8, BI_RLE4
unsigned int biSizeImage; // Specifies the size, in bytes, of the image. It is valid to set this member to zero if the bitmap is in the BI_RGB format.
int biXPelsPerMeter; // Specifies the horizontal resolution, in pixels per meter, of the target device for the bitmap.
int biYPelsPerMeter; // Specifies the vertical resolution, in pixels per meter, of the target device for the bitmap.
unsigned int biClrUsed; // Specifies the number of color indexes in the color table actually used by the bitmap.
unsigned int biClrImportant; // Specifies the number of color indexes that are considered important for displaying the bitmap. If this value is zero, all colors are important.
} BITMAPINFOHEADER;
typedef struct tagRGBPIXEL{
unsigned char b;
unsigned char g;
unsigned char r;
} rgbPIXEL;
#pragma pack(pop)
typedef struct tagBITMAP{
BITMAPFILEHEADER FILEHEADER;
BITMAPINFOHEADER INFOHEADER;
rgbPIXEL* IMAGEDATA;
}BITMAP;
void main(){
string sImageLocation = "C:/BMP.bmp";
BITMAP bmpImage;
FILE* fbmpImage = NULL;
unsigned int ImagePixelAmount = 0;
bool bImageLoaded = false;
do{
//Open the image file
fopen_s(&fbmpImage, sImageLocation.c_str(), "rb");
//Check whether the image could be loaded successfully or not
if(fbmpImage == NULL){
cout << "Loading the image file failed!" << " " << endl;
}
if(fbmpImage != NULL){
cout << "Loaded the image file successfully!" << endl;
bImageLoaded = true;
}
cout << endl;
cout << endl;
cout << endl;
//Read the BITMAP FILE HEADER
fseek(fbmpImage, 0, SEEK_SET);
fread(&bmpImage.FILEHEADER, sizeof(BITMAPFILEHEADER), 1, fbmpImage);
//Check if the image is a valid bitmap file
if(bmpImage.FILEHEADER.bfType != 19778){
bImageLoaded = false;
cout << "Image is not a valid Bitmap file!" << endl;
fclose(fbmpImage);
}
}while(bImageLoaded = false);
//Show the information of the BITMAP FILE HEADER in the consol
cout << "Bitmap File Header Data Values:" << endl;
cout << endl;
cout << "Image Type: " << bmpImage.FILEHEADER.bfType << endl;
cout << "Image Size: " << bmpImage.FILEHEADER.bfSize << " Bytes" << endl;
cout << "Reserved: " << bmpImage.FILEHEADER.bfReserved1 << endl;
cout << "Reserved: " << bmpImage.FILEHEADER.bfReserved2 << endl;
cout << "Byte Offset: " << bmpImage.FILEHEADER.bfOffBits << endl;
cout << endl;
cout << endl;
cout << endl;
//Read the BITMAP INFO HEADER
fread(&bmpImage.INFOHEADER, sizeof(BITMAPINFOHEADER), 1, fbmpImage);
cout << "Bitmap Info Header Data Values: " << endl;
cout << endl;
cout << "Size of Bitmap Info Header: " << bmpImage.INFOHEADER.biSize << " Bytes" << endl;
cout << "Width of Bitmap: " << bmpImage.INFOHEADER.biWidth << " Pixel" << endl;
cout << "Height of Bitmap: " << bmpImage.INFOHEADER.biHeight << " Pixel" << endl;
cout << "Size of Image Data: " << bmpImage.INFOHEADER.biHeight << " Bytes" << endl;
cout << "Bit Count: " << bmpImage.INFOHEADER.biBitCount << " Bits Per Pixel" << endl;
cout << "Amount of color indexes: " << bmpImage.INFOHEADER.biClrUsed << endl;
cout << "Compression: " << bmpImage.INFOHEADER.biCompression << endl;
cout << endl;
cout << endl;
cout << endl;
ImagePixelAmount = bmpImage.INFOHEADER.biHeight * bmpImage.INFOHEADER.biWidth;
//Create space in memory and read in pixel data from the image
bmpImage.IMAGEDATA = (rgbPIXEL*)malloc(sizeof(rgbPIXEL) * ImagePixelAmount);
cout << "Memory for image created" << endl;
fseek(fbmpImage, bmpImage.FILEHEADER.bfOffBits, SEEK_SET);
fread(bmpImage.IMAGEDATA, ImagePixelAmount * sizeof(rgbPIXEL), 1, fbmpImage);
fclose(fbmpImage);
//Show the pixel data in the consol in numbers instead of ASCII-symbols
for(int y =0; y < bmpImage.INFOHEADER.biHeight; y++){
for(int x = 0; x < bmpImage.INFOHEADER.biWidth; x++){
cout << "Red: " <<(unsigned int) bmpImage.IMAGEDATA[y * bmpImage.INFOHEADER.biWidth + x].r << " ";
cout << "Green: " <<(unsigned int) bmpImage.IMAGEDATA[y * bmpImage.INFOHEADER.biWidth + x].g << " ";
cout << "Blue: " <<(unsigned int) bmpImage.IMAGEDATA[y * bmpImage.INFOHEADER.biWidth + x].b << " ";
}
cout << endl;
}
cout << endl;
cout << endl;
cout << endl;
cout << "Press any key to quit the programm" << endl;
_getch();
return;
}
更新：
根據Hans Passant，我將我的代碼更改爲加載24位位圖。使用紅色位圖，我會假設每個像素的打印值是red = 255, green = 0 and blue = 0。然而，我收到的每個像素的實際值是red = 237, green = 28 and blue = 36。與其他圖像我有同樣的麻煩。
是否bmpImage。INFOHEADER.biSizeImage == ImagePixelAmount * sizeof（int）; ？ –
對古代圖像格式的不懈追求是不可阻擋的，8bpp只在20年前變得至關重要。你的malloc（）調用是錯誤的，8bpp圖像中的一個像素是一個字節，而不是'unsigned int'。而一張8bpp圖片有一張顏色表。 –
謝謝你的答案！ @PierreEmmanuelLallemant：可悲的是，情況並非如此。 – StirriX