C语言实现BMP图像B分量直方图均衡化

#include <stdio.h>
#include <stdlib.h>

#pragma pack(1)

typedef struct {
    unsigned short type;
    unsigned int size;
    unsigned short reserved1;
    unsigned short reserved2;
    unsigned int offset;
} BMPFileHeader;

typedef struct {
    unsigned int size;
    int width;
    int height;
    unsigned short planes;
    unsigned short bitsPerPixel;
    unsigned int compression;
    unsigned int imageSize;
    int xPixelsPerMeter;
    int yPixelsPerMeter;
    unsigned int colorsUsed;
    unsigned int colorsImportant;
} BMPInfoHeader;

typedef struct {
    unsigned char blue;
    unsigned char green;
    unsigned char red;
} BMPColor;

int main() {
    FILE* file = fopen('3.bmp', 'rb');
    if (!file) {
        printf("Failed to open file.\n");
        return 1;
    }

    BMPFileHeader fileHeader;
    fread(&fileHeader, sizeof(fileHeader), 1, file);

    BMPInfoHeader infoHeader;
    fread(&infoHeader, sizeof(infoHeader), 1, file);

    BMPColor* colors = (BMPColor*) malloc(sizeof(BMPColor) * infoHeader.width * infoHeader.height);
    fread(colors, sizeof(BMPColor), infoHeader.width * infoHeader.height, file);

    fclose(file);

    // Calculate histogram
    int histogram[256] = {0};
    for (int i = 0; i < infoHeader.width * infoHeader.height; i++) {
        histogram[colors[i].blue]++;
    }

    // Calculate cumulative distribution function
    int cdf[256] = {0};
    int sum = 0;
    for (int i = 0; i < 256; i++) {
        sum += histogram[i];
        cdf[i] = sum;
    }

    // Compute equalization map
    int map[256] = {0};
    float factor = 255.0 / (infoHeader.width * infoHeader.height);
    for (int i = 0; i < 256; i++) {
        map[i] = (int)(cdf[i] * factor + 0.5);
    }

    // Apply equalization map to blue component
    for (int i = 0; i < infoHeader.width * infoHeader.height; i++) {
        colors[i].blue = map[colors[i].blue];
    }

    // Write output file
    file = fopen('6.bmp', 'wb');
    if (!file) {
        printf("Failed to create output file.\n");
        return 1;
    }

    fwrite(&fileHeader, sizeof(fileHeader), 1, file);
    fwrite(&infoHeader, sizeof(infoHeader), 1, file);
    fwrite(colors, sizeof(BMPColor), infoHeader.width * infoHeader.height, file);

    fclose(file);

    free(colors);

    return 0;
}