1.学习例子ex_bitmap_flip.c
2.一个显示位图翻转标志的例子
/* An example showing bitmap flipping flags, by Steven Wallace. */
#include
#include
#include
#include "common.c"
/* Fire the update every 10 milliseconds. */
#define INTERVAL 0.01
float bmp_x = 200; //起始坐标
float bmp_y = 200; //起始坐标
float bmp_dx = 96; //水平速度
float bmp_dy = 96; //垂直速度
int bmp_flag = 0;
/* Updates the bitmap velocity, orientation and position. */
static void update(ALLEGRO_BITMAP *bmp)
{
ALLEGRO_BITMAP *target = al_get_target_bitmap(); /*全屏位图*/
int display_w = al_get_bitmap_width(target);
int display_h = al_get_bitmap_height(target);
int bitmap_w = al_get_bitmap_width(bmp);
int bitmap_h = al_get_bitmap_height(bmp);
bmp_x += bmp_dx * INTERVAL;
bmp_y += bmp_dy * INTERVAL;
/* Make sure bitmap is still on the screen. */
/*ALLEGRO_FLIP_VERTICAL=2*/
/*~ALLEGRO_FLIP_VERTICAL=01*/
/*bmp_flag &= 01就是把bit2变0*/
/*将垂直翻转状态置0*/
/*结果就是在上边时候垂直不翻转*/
if (bmp_y < 0) {
bmp_y = 0;
bmp_dy *= -1;
bmp_flag &= ~ALLEGRO_FLIP_VERTICAL; /*2,1,0*/
//printf("bmp_y ALLEGRO_FLIP_VERTICAL=%d bmp_flag=%d\n", ALLEGRO_FLIP_VERTICAL, bmp_flag);
}
/*ALLEGRO_FLIP_HORIZONTAL=1*/
/*~ALLEGRO_FLIP_HORIZONTAL=0*/
/*bmp_flag &= 0就是把bit1变0*/
/*将水平翻转状态置0*/
/*结果就是在左边时候水平不翻转*/
if (bmp_x < 0) {
bmp_x = 0;
bmp_dx *= -1;
bmp_flag &= ~ALLEGRO_FLIP_HORIZONTAL;
//printf("bmp_x ALLEGRO_FLIP_HORIZONTAL=%d bmp_flag=%d\n", ALLEGRO_FLIP_HORIZONTAL, bmp_flag);
}
/*ALLEGRO_FLIP_VERTICAL=2*/
/*bmp_flag |= 10就是把bit2变1*/
/*将垂直翻转状态置1*/
/*结果就是在下边时候垂直翻转*/
if (bmp_y > display_h - bitmap_h) {
bmp_y = display_h - bitmap_h;
bmp_dy *= -1;
bmp_flag |= ALLEGRO_FLIP_VERTICAL;
//printf("bmp_y2 ALLEGRO_FLIP_VERTICAL=%d bmp_flag=%d\n", ALLEGRO_FLIP_VERTICAL, bmp_flag);
}
/*ALLEGRO_FLIP_HORIZONTAL=1*/
/*bmp_flag |= 1就是把bit1变1*/
/*将水平翻转状态置1*/
/*结果就是在右边时候水平翻转*/
if (bmp_x > display_w - bitmap_w) {
bmp_x = display_w - bitmap_w;
bmp_dx *= -1;
bmp_flag |= ALLEGRO_FLIP_HORIZONTAL;
//printf("bmp_x2 ALLEGRO_FLIP_HORIZONTAL=%d bmp_flag=%d\n", ALLEGRO_FLIP_HORIZONTAL, bmp_flag);
}
}
int main(int argc, char **argv)
{
ALLEGRO_DISPLAY *display;
ALLEGRO_TIMER *timer;
ALLEGRO_EVENT_QUEUE *queue;
ALLEGRO_BITMAP *bmp;
ALLEGRO_BITMAP *mem_bmp;
ALLEGRO_BITMAP *disp_bmp;
ALLEGRO_FONT *font;
char *text;
bool done = false;
bool redraw = true;
/* Silence unused arguments warnings. */
(void)argc;
(void)argv;
if (!al_init()) {
abort_example("Failed to init Allegro.\n");
}
/* Initialize the image addon. Requires the allegro_image addon
* library.
*/
if (!al_init_image_addon()) {
abort_example("Failed to init IIO addon.\n");
}
/* Initialize the image font. Requires the allegro_font addon
* library.
*/
al_init_font_addon();
init_platform_specific(); /* Helper functions from common.c. */
/* Create a new display that we can render the image to. */
display = al_create_display(640, 480);
if (!display) {
abort_example("Error creating display.\n");
}
/* Allegro requires installing drivers for all input devices before
* they can be used.
*/
if (!al_install_keyboard()) {
abort_example("Error installing keyboard.\n");
}
/* Loads a font from disk. This will use al_load_bitmap_font if you
* pass the name of a known bitmap format, or else al_load_ttf_font.
*/
font = al_load_font("data/fixed_font.tga", 0, 0);
if (!font) {
abort_example("Error loading data/fixed_font.tga\n");
}
bmp = disp_bmp = al_load_bitmap("data/mysha.pcx");
if (!bmp) {
abort_example("Error loading data/mysha.pcx\n");
}
text = "Display bitmap (space to change)";
/*创建驻留在系统内存中的位图*/
al_set_new_bitmap_flags(ALLEGRO_MEMORY_BITMAP);
mem_bmp = al_load_bitmap("data/mysha.pcx");
if (!mem_bmp) {
abort_example("Error loading data/mysha.pcx\n");
}
/*创建定时器*/
timer = al_create_timer(INTERVAL);
queue = al_create_event_queue();
al_register_event_source(queue, al_get_keyboard_event_source());
al_register_event_source(queue, al_get_timer_event_source(timer));
al_register_event_source(queue, al_get_display_event_source(display));
/*启动定时器*/
al_start_timer(timer);
/* Default premultiplied aplha blending. */
al_set_blender(ALLEGRO_ADD, ALLEGRO_ONE, ALLEGRO_INVERSE_ALPHA);
/* Primary 'game' loop. */
while (!done) {
ALLEGRO_EVENT event;
/* If the timer has since been fired and the queue is empty, draw.*/
if (redraw && al_is_event_queue_empty(queue)) {
update(bmp);
/* Clear so we don't get trippy artifacts left after zoom. */
al_clear_to_color(al_map_rgb_f(0, 0, 0));
al_draw_tinted_bitmap(bmp, al_map_rgba_f(1, 1, 1, 0.5),
bmp_x, bmp_y, bmp_flag);
/*bmp_flag=0表示不翻转,*/
/*bmp_flag=1表示ALLEGRO_FLIP_HORIZONTAL,水平翻转*/
/*bmp_flag=2表示ALLEGRO_FLIP_VERTICAL,垂直翻转*/
/*bmp_flag=3表示ALLEGRO_FLIP_HORIZONTAL+ALLEGRO_FLIP_VERTICAL,水平翻转+垂直翻转*/
al_draw_text(font, al_map_rgba_f(1, 1, 1, 0.5), 0, 0, 0, text);
al_flip_display();
redraw = false;
}
al_wait_for_event(queue, &event);
switch (event.type) {
case ALLEGRO_EVENT_KEY_DOWN:
if (event.keyboard.keycode == ALLEGRO_KEY_ESCAPE)
done = true;
else if (event.keyboard.keycode == ALLEGRO_KEY_SPACE) {
/* Spacebar toggles whether render from a memory bitmap
* or display bitamp.
*/
if (bmp == mem_bmp) {
bmp = disp_bmp;
text = "Display bitmap (space to change)";
}
else {
bmp = mem_bmp;
text = "Memory bitmap (space to change)";
}
}
break;
case ALLEGRO_EVENT_DISPLAY_CLOSE:
done = true;
break;
case ALLEGRO_EVENT_TIMER:
redraw = true;
break;
}
}
al_destroy_bitmap(bmp);
return 0;
}
/* vim: set sts=3 sw=3 et: */
3.运行效果
1AFF2873-C3E1-46D7-8311-4A2DF57867FA.png
4.代码地址