sysy-data/hidden_functional_c/sy/36_rotate.sy

#include "sylib.h"

#include <string.h>

#define MAX_WIDTH 1024
// const int MAX_WIDTH = 1024
#define MAX_HEIGHT 1024
int image[MAX_WIDTH * MAX_HEIGHT], width, height;

const float PI = 3.14159265359, TWO_PI = 6.28318530718, EPSILON = 1e-6;

float my_fabs(float x)
{
    if (x > 0) {
        return x;
    }
    return -x;
}

float p(float x) { return 3 * x - 4 * x * x * x; }

float my_sin_impl(float x)
{
    if (my_fabs(x) <= EPSILON) {
        return x;
    }
    return p(my_sin_impl(x / 3.0));
}

float my_sin(float x)
{
    if (x > TWO_PI || x < -TWO_PI) {
        int xx = x / TWO_PI;
        x = x - xx * TWO_PI;
    }
    if (x > PI) {
        x = x - TWO_PI;
    }
    if (x < -PI) {
        x = x + TWO_PI;
    }
    return my_sin_impl(x);
}

float my_cos(float x) { return my_sin(x + PI / 2); }

int read_image()
{
    if (getch() != 80 || getch() != 50)
        return -1;
    width = getint();
    height = getint();
    if (width > MAX_WIDTH || height > MAX_HEIGHT || getint() != 255)
        return -1;
    int y = 0;
    while (y < height) {
        int x = 0;
        while (x < width) {
            image[y * width + x] = getint();
            x = x + 1;
        }
        y = y + 1;
    }
    return 0;
}

int rotate(int x, int y, float rad)
{
    float sinma = my_sin(rad), cosma = my_cos(rad);
    int hwidth = width / 2, hheight = height / 2;
    int xt = x - hwidth, yt = y - hheight;
    int src_x = xt * cosma - yt * sinma + hwidth,
        src_y = xt * sinma + yt * cosma + hheight;
    if (src_x < 0 || src_x >= width || src_y < 0 || src_y >= height)
        return 0;
    return image[src_y * width + src_x];
}

void write_pgm(float rad)
{
    putch(80);
    putch(50);
    putch(10); // P2
    putint(width);
    putch(32);
    putint(height);
    putch(32); // width height
    putint(255);
    putch(10); // 255
    int y = 0;
    while (y < height) {
        int x = 0;
        while (x < width) {
            putint(rotate(x, y, rad));
            putch(32);
            x = x + 1;
        }
        putch(10);
        y = y + 1;
    }
}

int main()
{
    memset(image, 0, MAX_WIDTH * MAX_HEIGHT);
    float rad = getfloat();
    getch();
    if (read_image() < 0)
        return -1;
    write_pgm(rad);
    return 0;
}