1 2#define _USE_MATH_DEFINES 3 4#include <allegro5/allegro.h> 5#include <allegro5/allegro_image.h> 6#include <math.h> 7 8#define DEG_TO_RAD(deg) (deg*M_PI/180.0) 9 10int main() 11{ 12 al_init(); 13 al_init_image_addon(); 14 15 al_set_new_display_flags(ALLEGRO_WINDOWED); 16 ALLEGRO_DISPLAY* display = al_create_display(1280, 720); 17 18 //Load the test image 19 ALLEGRO_BITMAP* image = al_load_bitmap("test_image.png"); 20 21 //Get the test image width/height 22 int image_w = al_get_bitmap_width(image); 23 int image_h = al_get_bitmap_height(image); 24 25 //Work out the largest dimenstion (width or height) 26 int image_largest_size = image_w > image_h ? image_w : image_h; 27 28 //Create a new bitmap with the largest dimension for width height (to fit out rotated image) 29 ALLEGRO_BITMAP* rotated_image = al_create_bitmap(image_largest_size, image_largest_size); 30 31 //Set the new bitmap as target 32 al_set_target_bitmap(rotated_image); 33 34 //Draw the test image rotated by 45 degrees 35 al_draw_rotated_bitmap(image, image_w / 2, image_h / 2, image_largest_size / 2, image_largest_size / 2, DEG_TO_RAD(45), 0); 36 37 //Set the display as target 38 al_set_target_backbuffer(display); 39 40 //Save the rotated image 41 al_save_bitmap("rotated_image_saved.png", rotated_image); 42 43 //Cleanup 44 al_destroy_bitmap(image); 45 al_destroy_bitmap(rotated_image); 46 al_destroy_display(display); 47}

1 2#define _USE_MATH_DEFINES 3 4#include <allegro5/allegro.h> 5#include <allegro5/allegro_image.h> 6#include <math.h> 7 8#define DEG_TO_RAD(deg) (deg*M_PI/180.0) 9 10struct size 11{ 12 int width; 13 int height; 14}; 15 16size get_rotated_image_size(int orig_width, int orig_height, int degrees); 17 18int main() 19{ 20 al_init(); 21 al_init_image_addon(); 22 23 al_set_new_display_flags(ALLEGRO_WINDOWED); 24 ALLEGRO_DISPLAY* display = al_create_display(1280, 720); 25 26 //Load the test image 27 ALLEGRO_BITMAP* image = al_load_bitmap("test_image.png"); 28 29 //Get the test image width/height 30 int image_w = al_get_bitmap_width(image); 31 int image_h = al_get_bitmap_height(image); 32 33 //Work out the largest dimenstion (width or height) 34 int image_largest_size = image_w > image_h ? image_w : image_h; 35 36 //Set rotation 37 int degrees = 45; 38 39 size rotated_image_size = get_rotated_image_size(image_w, image_h, degrees); 40 41 //Create a new bitmap with the largest dimension for width height (to fit out rotated image) 42 ALLEGRO_BITMAP* rotated_image = al_create_bitmap(rotated_image_size.width, rotated_image_size.height); 43 44 //Set the new bitmap as target 45 al_set_target_bitmap(rotated_image); 46 47 //Draw the test image rotated by 45 degrees 48 al_draw_rotated_bitmap(image, image_w / 2, image_h / 2, rotated_image_size.width / 2, rotated_image_size.height / 2, DEG_TO_RAD(degrees), 0); 49 50 //Set the display as target 51 al_set_target_backbuffer(display); 52 53 //Save the rotated image 54 al_save_bitmap("rotated_image_saved.png", rotated_image); 55 56 //Cleanup 57 al_destroy_bitmap(image); 58 al_destroy_bitmap(rotated_image); 59 al_destroy_display(display); 60} 61 62size get_rotated_image_size(int orig_width, int orig_height, int degrees) { 63 degrees = degrees % 180; 64 65 if (degrees < 0) { 66 degrees = 180 + degrees; 67 } 68 if (degrees >= 90) { 69 int copy_orig_height = orig_height; 70 orig_height = orig_width; 71 orig_width = copy_orig_height; 72 degrees = degrees - 90; 73 } 74 if (degrees == 0) { 75 size new_image_size; 76 new_image_size.width = orig_width; 77 new_image_size.height = orig_height; 78 return new_image_size; 79 } 80 81 float radians = DEG_TO_RAD(degrees); 82 int width = ceil((orig_width * cos(radians)) + (orig_height * sin(radians))); 83 int height = ceil((orig_width * sin(radians)) + (orig_height * cos(radians))); 84 85 size new_image_size; 86 new_image_size.width = width; 87 new_image_size.height = height; 88 return new_image_size; 89}