w6

未完成的台灣國旗

// https://en.wikipedia.org/wiki/Flag_of_the_Republic_of_China
// cc roc_flag.c -lgd -lm to link with gd and math library
// https://www.rapidtables.com/web/color/RGB_Color.html
// 幾何形狀著色與繪圖練習
// 以下 gd 繪圖程式嘗試畫出 ROC 國旗, 請根據下列程式內容完成後續的國旗繪圖
#include <stdio.h>
#include <gd.h>
#include <math.h>
 
void draw_roc_flag(gdImagePtr img);
void draw_white_sun(gdImagePtr img, int x, int y, int size, int color);
 
int main() {
    // width 3: height 2
    int width = 1200;
    int height = (int)(width*2.0 / 3.0);
 
    gdImagePtr img = gdImageCreateTrueColor(width, height);
    gdImageAlphaBlending(img, 0);
 
    draw_roc_flag(img);
 
    FILE *outputFile = fopen("./../images/roc_flag.png", "wb");
    if (outputFile == NULL) {
        fprintf(stderr, "Error opening the output file.\n");
        return 1;
    }
    gdImagePngEx(img, outputFile, 9);
    fclose(outputFile);
    gdImageDestroy(img);
    return 0;
}
 
void draw_roc_flag(gdImagePtr img) {
    int width = gdImageSX(img);
    int height = gdImageSY(img);
    int red, white, blue;
    int center_x = (int)(width/4);
    int center_y = (int)(height/4);
    int sun_radius = (int)(width/8);
    // Colors for the flag
    red = gdImageColorAllocate(img, 242, 0, 0); // Red color
    white = gdImageColorAllocate(img, 255, 255, 255); // White stripes
    blue = gdImageColorAllocate(img, 0, 41, 204); // Blue
    // red rectangle area
    gdImageFilledRectangle(img, 0, 0, width, height, red);
    // blue rectangle area
    gdImageFilledRectangle(img, 0, 0, (int)(width/2.0), (int)(height/2.0), blue);
    // 目前僅畫出青天白日的輪廓直線, 請嘗試計算所需的點座標完成國旗繪圖
    draw_white_sun(img, center_x, center_y, sun_radius, white);
}
 
void draw_white_sun(gdImagePtr img, int center_x, int center_y, int sun_radius, int color) {
    float angle = 0;
    int fromX, fromY;
    int toX, toY;
    for (int i=0; i<24; i++){
        angle += 5*M_PI*2/12;
        //printf("%.3f", angle);
        toX = center_x + cos(angle)*sun_radius;
        toY = center_y + sin(angle)*sun_radius;
        // 只有 i 為 0 時移動到 toX, toY, 其餘都進行直線繪圖
        if (i!=0){
            gdImageLine(img, fromX, fromY, toX, toY, color);
        }
        fromX = toX;
        fromY = toY;
   }
}

未完成的美國國旗

// https://en.wikipedia.org/wiki/Flag_of_the_United_States
// https://www.britannica.com/topic/flag-of-the-United-States-of-America
// 以下為幾乎要繪製完成的美國國旗, 請修改下列原始碼, 令其繪出正確的美國國旗
#include <stdio.h>
#include <gd.h>
#include <math.h>
 
void draw_usa_flag(gdImagePtr img);
void draw_star(gdImagePtr img, int x, int y, int size, int color);
 
int main() {
    int width = 800;
    int height = (int)(width / 1.9);
 
    gdImagePtr img = gdImageCreateTrueColor(width, height);
    gdImageAlphaBlending(img, 0);
 
    draw_usa_flag(img);
 
    FILE *outputFile = fopen("./../images/usa_flag.png", "wb");
    if (outputFile == NULL) {
        fprintf(stderr, "Error opening the output file.\n");
        return 1;
    }
 
    gdImagePngEx(img, outputFile, 9);
    fclose(outputFile);
    gdImageDestroy(img);
 
    return 0;
}
 
void draw_usa_flag(gdImagePtr img) {
    int width = gdImageSX(img);
    int height = gdImageSY(img);
    int red, white, blue;
    // Colors for the flag
    red = gdImageColorAllocate(img, 178, 34, 52); // Red stripes
    white = gdImageColorAllocate(img, 255, 255, 255); // White stripes
    blue = gdImageColorAllocate(img, 60, 59, 110); // Blue field
 
    int stripe_height = height / 13;
    int stripe_width = width;
    int star_size = (int)(0.0308 * height); // Corrected star size (half the original size)
 
    for (int y = 0; y < height; y += stripe_height) {
        if (y / stripe_height % 2 == 0) {
            gdImageFilledRectangle(img, 0, y, stripe_width, y + stripe_height, red);
        } else {
            gdImageFilledRectangle(img, 0, y, stripe_width, y + stripe_height, white);
        }
    }
 
    gdImageFilledRectangle(img, 0, 0, width * 2 / 5, stripe_height * 7, blue);
 
    int star_spacing_x = (int)(0.063 * height); // Horizontal spacing between stars
    int star_spacing_y = (int)(0.054 * height); // Vertical spacing between stars
    int star_start_x = (int)(0.0616 * height); // Starting X position for stars
    int star_start_y = (int)(0.0485 * height); // Starting Y position for stars
 
    for (int row = 0; row < 9; row++) {
        int starsPerRow = (row % 2 == 0) ? 6 : 5;
 
        for (int star = 0; star < starsPerRow; star++) {
            int x = star_start_x + star * star_spacing_x;
            int y = star_start_y + row * star_spacing_y;
            draw_star(img, x, y, star_size, white);
        }
    }
}
 
void draw_star(gdImagePtr img, int x, int y, int size, int color) {
    gdPoint points[10];
 
    for (int i = 0; i < 10; i++) {
        double angle = M_PI / 2 + i * 2 * M_PI / 10;
        int radius = (i % 2 == 0) ? size : size / 2;
        points[i].x = x + radius * cos(angle);
        points[i].y = y + radius * sin(angle);
    }
 
    // Fill the star with white color
    gdImageFilledPolygon(img, points, 10, color);
}

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