#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <math.h>
typedef unsigned char uch;


// 檔案結構
#pragma pack(2)
struct BmpFileHeader {
    uint16_t bfTybe;
    uint32_t bfSize;
    uint16_t bfReserved1;
    uint16_t bfReserved2;
    uint32_t bfOffBits;
};
struct BmpInfoHeader {
    uint32_t biSize;
    uint32_t biWidth;
    uint32_t biHeight;
    uint16_t biPlanes; // 1=defeaul, 0=custom
    uint16_t biBitCount;
    uint32_t biCompression;
    uint32_t biSizeImage;
    uint32_t biXPelsPerMeter; // 72dpi=2835, 96dpi=3780
    uint32_t biYPelsPerMeter; // 120dpi=4724, 300dpi=11811
    uint32_t biClrUsed;
    uint32_t biClrImportant;
};
#pragma pack()

//辅助计算函数
float linear_single(float x, float x1, float x2, float f1, float f2){
    return floor(f1 * (x2 - x) / (x2 - x1) + f2 * (x - x1) / (x2 - x1));
}

// 双线性插值函数
// 参考 https://zh.wikipedia.org/wiki/%E5%8F%8C%E7%BA%BF%E6%80%A7%E6%8F%92%E5%80%BC
char linear_insert(uch** old_pixels, uint32_t row, uint32_t col, uint32_t old_width, uint32_t old_height, float radio_w, float radio_h){
    float x = row / radio_h;
    float y = col / radio_w;
    // 如果整数格点就直接返回
    int x1 = floor(x);
    int x2 = ceil(x);
    int y1 = floor(y);
    int y2 = ceil(y);
    if (x2 >= old_height){x2 = x1;}
        
    if (y2 >= old_width){y2 = y1;}
    if (x1 == x2 && y1 == y2){return old_pixels[x1][y1];}
    if (x1 == x2){
        int x = x1;
        uint32_t idx1 = x*old_width+y;
        uint32_t idx2 = x*old_width+y;
        float r = linear_single(y, y1, y2, old_pixels[x][idx1 + 0], old_pixels[x][idx2 + 0]);
        float g = linear_single(y, y1, y2, old_pixels[x][idx1 + 1], old_pixels[x][idx2 + 1]);
        float b = linear_single(y, y1, y2, old_pixels[x][idx1 + 2], old_pixels[x][idx2 + 2]);
        return (char)r, (char)g, (char)b;
    }
    if (y1 == y2){
        int y = y1;
        uint32_t idx = x*old_width+y;
        float r = linear_single(x, x1, x2, old_pixels[x1][idx + 0], old_pixels[x2][idx + 0]);
        float g = linear_single(x, x1, x2, old_pixels[x1][idx + 1], old_pixels[x2][idx + 1]);
        float b = linear_single(x, x1, x2, old_pixels[x1][idx + 2], old_pixels[x2][idx + 2]);
        return (char)r, (char)g, (char)b;
    }
    uint32_t idx1 = x*old_width+y;
    uint32_t idx2 = x*old_width+y;
    float fy1_r = linear_single(x, x1, x2, old_pixels[x1][idx1 + 0], old_pixels[x2][idx1 + 0]);
    float fy1_g = linear_single(x, x1, x2, old_pixels[x1][idx1 + 1], old_pixels[x2][idx1 + 1]);
    float fy1_b = linear_single(x, x1, x2, old_pixels[x1][idx1 + 2], old_pixels[x2][idx1 + 2]);
    float fy2_r = linear_single(x, x1, x2, old_pixels[x1][idx2 + 0], old_pixels[x2][idx2 + 0]);
    float fy2_g = linear_single(x, x1, x2, old_pixels[x1][idx2 + 1], old_pixels[x2][idx2 + 1]);
    float fy2_b = linear_single(x, x1, x2, old_pixels[x1][idx2 + 2], old_pixels[x2][idx2 + 2]);
    float r = linear_single(y, y1, y2, fy1_r, fy2_r);
    float g = linear_single(y, y1, y2, fy1_g, fy2_g);
    float b = linear_single(y, y1, y2, fy1_b, fy2_b);
    return (char)r, (char)g, (char)b;
}

void bmpWrite(const char* name, const uch* raw_img, uint32_t width, uint32_t height, uint32_t bits, float radio_w, float radio_h){
    if(!(name && raw_img)){
        perror("Error bmpWrite.");
        return;
    }
    // 檔案資訊
    struct BmpFileHeader file_h = {
        .bfTybe=0x4d42,
        .bfReserved1=0,
        .bfReserved2=0,
        .bfOffBits=54,
    };

    uint32_t new_width = floor(width*radio_w);
    uint32_t new_height = floor(height*radio_h);
    file_h.bfSize = file_h.bfOffBits + new_width*new_height * bits/8;
    if(bits==8) {file_h.bfSize+= 1024, file_h.bfOffBits+= 1024;}


    // 圖片資訊
    struct BmpInfoHeader info_h = {
        .biSize=40,
        .biPlanes=1,
        .biCompression=0,
        .biXPelsPerMeter=0,
        .biYPelsPerMeter=0,
        .biClrUsed=0,
        .biClrImportant=0,
    };
    info_h.biWidth = new_width;
    info_h.biHeight = new_height;
    info_h.biBitCount = bits;// 多少位的圖
    info_h.biSizeImage = new_width*new_height * bits/8;
    if(bits == 8) {info_h.biClrUsed=256;}
    // 寫入檔頭
    FILE *pFile = NULL;
    // pFile = fopen(name,"wb+");
    fopen_s(&pFile, name,"wb+");
    if(!pFile) {
        perror("Error opening file.");
        return;
    }
    fwrite((char*)&file_h, sizeof(char), sizeof(file_h), pFile);
    fwrite((char*)&info_h, sizeof(char), sizeof(info_h), pFile);
    // 寫調色盤
    if(bits == 8) {
        for(unsigned i = 0; i < 256; ++i) {
            uch c = i;
            fwrite((char*)&c, sizeof(char), sizeof(uch), pFile);
            fwrite((char*)&c, sizeof(char), sizeof(uch), pFile);
            fwrite((char*)&c, sizeof(char), sizeof(uch), pFile);
            fwrite("", sizeof(char), sizeof(uch), pFile);
        }
    }

    // char newpixels[new_width*new_height];
    unsigned char **newpixels=(unsigned char**)malloc(new_width*new_height*3);// 沒用到
	
    // 寫入圖片資訊
    size_t alig = ((new_width*bits/8)*3) % 4;
    // for(int j = new_height-1; j >= 0; --j) {
    //     for(unsigned i = 0; i < new_width; ++i) {
    //         uint32_t idx = j*new_width +i;
    //         if(bits == 24) { // RGB圖片
    //             fwrite((char*)&raw_img[idx*3 +2], sizeof(char), sizeof(uch), pFile);
    //             fwrite((char*)&raw_img[idx*3 +1], sizeof(char), sizeof(uch), pFile);
    //             fwrite((char*)&raw_img[idx*3 +0], sizeof(char), sizeof(uch), pFile);
    //         } else if(bits == 8) { // 灰階圖
    //             fwrite((char*)&raw_img[idx], sizeof(char), sizeof(uch), pFile);
    //         }
    //     }


    for(int j = new_height-1; j >= 0; --j) {
        for(unsigned i = 0; i < new_width; ++i) {
            uint32_t idx = j*new_width +i;
            if(bits == 24) { // RGB圖片
                char* r, g, b = linear_insert(&raw_img, j, i, width, height, radio_w, radio_h);
                fwrite(b, sizeof(char), sizeof(uch), pFile);
                fwrite(g, sizeof(char), sizeof(uch), pFile);
                fwrite(r, sizeof(char), sizeof(uch), pFile);
            } else if(bits == 8) { // 灰階圖
                fwrite((char*)&raw_img[idx], sizeof(char), sizeof(uch), pFile);
            }
        }
        //# 计算新像素
        // 對齊4byte
        for(size_t i = 0; i < alig; ++i) {
            fwrite("", sizeof(char), sizeof(uch), pFile);
        }
    }
    fclose(pFile);

    free(newpixels); //記得釋放空間
}
void bmpRead(const char* name, uch** oldpixels, uint32_t* width, uint32_t* height, uint16_t* bits)
{
    if(!(name && oldpixels && width && height && bits)) {
        perror("Error bmpRead.");
        return;
    }
    // 檔案資訊
    struct BmpFileHeader file_h;
    // 圖片資訊
    struct BmpInfoHeader info_h;
    // 讀取檔頭
    FILE *pFile = NULL;
    // pFile = fopen(name, "rb+");
    fopen_s(&pFile, name, "rb+");
    if(!pFile) {
        perror("Error opening file.");
        return;
    }
    fread((char*)&file_h, sizeof(char), sizeof(file_h), pFile);
    fread((char*)&info_h, sizeof(char), sizeof(info_h), pFile);
    // 讀取長寬
    *width = info_h.biWidth;
    *height = info_h.biHeight;
    *bits = info_h.biBitCount;
    unsigned char **oldpixels=(unsigned char**)malloc((*width)*(*height)*3);

    // size_t ImgSize = ((size_t)*width) * ((size_t)*height) * 3;
    // *raw_img = (uch*)calloc(ImgSize, sizeof(uch));
    // 讀取讀片資訊轉RAW檔資訊
    fseek(pFile, file_h.bfOffBits, SEEK_SET);
    size_t alig = ((info_h.biWidth*info_h.biBitCount/8)*3) % 4;
    for(int j = *height-1; j >= 0; --j) {
        for(unsigned i = 0; i < *width; ++i) {
            uint32_t idx = j*(*width)+i;
            if(*bits == 24) { // RGB圖片
                fread((char*)&(*oldpixels)[idx*3 +2], sizeof(char), sizeof(uch), pFile);
                fread((char*)&(*oldpixels)[idx*3 +1], sizeof(char), sizeof(uch), pFile);
                fread((char*)&(*oldpixels)[idx*3 +0], sizeof(char), sizeof(uch), pFile);
            } else if(*bits == 8) { // 灰階圖
                fread((char*)&(*oldpixels)[idx], sizeof(char), sizeof(uch), pFile);
            }
        }
        fseek(pFile , (long)alig , SEEK_CUR);
    }
    fclose(pFile);


//---------------------------------------------------------------------------
    // size_t ImgSize = ((size_t)*width) * ((size_t)*height) * 3;
    // *raw_img = (uch*)calloc(ImgSize, sizeof(uch));
    // // 讀取讀片資訊轉RAW檔資訊
    // fseek(pFile, file_h.bfOffBits, SEEK_SET);
    // size_t alig = ((info_h.biWidth*info_h.biBitCount/8)*3) % 4;
    // for(int j = *height-1; j >= 0; --j) {
    //     for(unsigned i = 0; i < *width; ++i) {
    //         uint32_t idx = j*(*width)+i;
    //         if(*bits == 24) { // RGB圖片
    //             fread((char*)&(*raw_img)[idx*3 +2], sizeof(char), sizeof(uch), pFile);
    //             fread((char*)&(*raw_img)[idx*3 +1], sizeof(char), sizeof(uch), pFile);
    //             fread((char*)&(*raw_img)[idx*3 +0], sizeof(char), sizeof(uch), pFile);
    //         } else if(*bits == 8) { // 灰階圖
    //             fread((char*)&(*raw_img)[idx], sizeof(char), sizeof(uch), pFile);
    //         }
    //     }
    //     fseek(pFile , (long)alig , SEEK_CUR);
    // }
    // fclose(pFile);
//----------------------------------------------------------------------------

    // for(int j = *height-1; j >= 0; --j) {
    //     for(unsigned i = 0; i < *width; ++i) {
    //         uint32_t idx = j*(*width)+i;
    //         for(int k = 0; k < 3; k++){
    //             printf((char*)&(*raw_img)[idx*3 + k]);
    //             printf("\t");
    //         }
    //         printf("\t done \t");
    //     }
    //     printf("\n");
    // }
}

// 圖像結構
typedef struct Imgraw {
    uint32_t width, height;
    uint16_t bits;
    uch* data;
} Imgraw;

void Imgraw_Read(const Imgraw* _this, const char* name) {
    const Imgraw* p = _this;
    bmpRead(name, &p->data, &p->width, &p->height, &p->bits);
}
void Imgraw_Writ(const Imgraw* _this, const char* name, float radio_w, float radio_h) {
    const Imgraw* p = _this;
    bmpWrite(name, p->data, p->width, p->height, p->bits, radio_w, radio_h);
}
/*==============================================================*/
int main(int argc, char const *argv[]) {
    float radio_w, radio_h;
    printf("Enter a radio of width :") ;
    scanf("%f", &radio_w);
    printf("Enter a radio of height :") ;
    scanf("%f", &radio_h);
    printf("%f :: %f\n", radio_w, radio_h);
    // 建構
    Imgraw img = {0, 0, 0, NULL};
    // 讀圖
    Imgraw_Read(&img, "./input/bw2x1.bmp");
    // 寫圖
    Imgraw_Writ(&img, "./output/bw2x1(output).bmp", radio_w, radio_h);
    return 0;
}
/*==============================================================*/