アンチエイリアス付きの自由線描画(1)

#include <math.h>
#include "sptk.h"

#define WIDTH  300
#define HEIGHT 300

SPTK_IMAGE *winimg;
SPTK_IMAGE32 *blendimg,*layerimg;

SPTK_POINT ptLast;
SPTK_PIX_RGBA drawcol = {b:0,0,0,64:b};
double line_radius = 3,
    line_interval = 0.15,
    line_last_t = 0;

/** 円を描画 */

void drawpoint(double x,double y,double radius)
{
    int nx1,ny1,nx2,ny2,ix,iy,jx,jy,cnt;
    double xx,yy,rr;
    SPTK_PIX_RGBA col;
    
    /* 描画先の範囲 */
    
    nx1 = (int)floor(x - radius);
    ny1 = (int)floor(y - radius);
    nx2 = (int)floor(x + radius);
    ny2 = (int)floor(y + radius);
    
    /* 描画先ループ */
    
    rr = radius * radius;
    
    for(iy = ny1; iy <= ny2; iy++)
    {
        for(ix = nx1; ix <= nx2; ix++)
        {
            /* オーバーサンプリング */
            
            cnt = 0;
            
            for(jy = 0; jy < 8; jy++)
            {
                yy = iy - y + jy * (1.0 / 8);
            
                for(jx = 0; jx < 8; jx++)
                {
                    xx = ix - x + jx * (1.0 / 8);
                    
                    if(xx * xx + yy * yy < rr)
                        cnt++;
                }
            }
            
            /* 結果 */
            
            col = drawcol;
            col.a = drawcol.a * cnt >> 6;
            
            sptk_image32_setpixel_rgba(layerimg, ix, iy, &col);
        }
    }
}

/** 直線描画 */

void drawline_aa(double x1,double y1,double x2,double y2,
    double radius,double *last_t)
{
    double dx,dy,len,t,t_interval,x,y,dtmp;
    
    /* 線の長さ */
    
    dx = x2 - x1;
    dy = y2 - y1;
    
    len = sqrt(dx * dx + dy * dy);
    if(len == 0) return;
    
    /* 線形補間 */
    
    t_interval = line_interval / len;
    
    t = *last_t / len;
    
    while(t < 1.0)
    {
        x = x1 + dx * t;
        y = y1 + dy * t;
        
        drawpoint(x, y, radius);
    
        /* 次の位置 */
    
        dtmp = radius * t_interval;
        if(dtmp < 0.0001) dtmp = 0.0001;
    
        t += dtmp;
    }
    
    *last_t = len * (t - 1.0);
}

/** 画面更新 */

void update_screen(SPTK_RECTWH *imgrc,int time)
{
    SPTK_RECTWH rc;
    
    if(imgrc)
        rc = *imgrc;
    else
        rc.x = 0, rc.y = 0, rc.w = WIDTH, rc.h = HEIGHT;
    
    sptk_image32_fill_plaid(blendimg, rc.x, rc.y, rc.w, rc.h);
    sptk_image32_blend_normal(blendimg, layerimg, rc.x, rc.y, rc.w, rc.h);

    sptk_image32_blt_image(blendimg, rc.x, rc.y, rc.w, rc.h, winimg, rc.x, rc.y);
    sptk_update(NULL, rc.x, rc.y, rc.w, rc.h, time);
}

/** ウィンドウハンドル */

void winhandle(SPTK_EVENT *ev)
{
    SPTK_RECT rc;
    SPTK_RECTWH rcwh;
    int r;

    switch(ev->type)
    {
        case SPTK_EVENT_BTTDOWN:
            if(ev->mouse.btt == SPTK_MOUSEBTT_LEFT)
            {
                ptLast.x = ev->mouse.x;
                ptLast.y = ev->mouse.y;
                            
                sptk_grab(NULL);
            }
            break;
        case SPTK_EVENT_BTTUP:
            if(ev->mouse.btt == SPTK_MOUSEBTT_LEFT && sptk_isgrab())
                sptk_ungrab();
            break;
        case SPTK_EVENT_MOUSEMOVE:
            if(sptk_isgrab())
            {            
                drawline_aa(ptLast.x, ptLast.y, ev->mouse.x, ev->mouse.y,
                        line_radius, &line_last_t);
            
                /* 更新 */

                rc.x1 = ptLast.x;
                rc.y1 = ptLast.y;
                rc.x2 = ev->mouse.x;
                rc.y2 = ev->mouse.y;
                
                sptk_rect_swap(&rc);
                
                r = (int)(line_radius + 0.5);
                
                rc.x1 -= r;
                rc.y1 -= r;
                rc.x2 += r;
                rc.y2 += r;
                
                if(!sptk_rect_clip_wh(&rc, WIDTH, HEIGHT))
                {
                    sptk_rect_to_rectwh(&rcwh, &rc);
                    
                    update_screen(&rcwh, 0);
                }
                
                ptLast.x = ev->mouse.x;
                ptLast.y = ev->mouse.y;
            }
            break;
        
        case SPTK_EVENT_WINDOW_KEYDOWN:
            if(ev->key.code == 'C')
            {
                /* クリア */
                
                sptk_image32_clear(layerimg, NULL);
                update_screen(NULL, -1);
            }
            else if(ev->key.code == 'T')
            {
                line_radius = 8;
                line_interval = 2.0;
                drawcol.a = 96;
            }
            break;
        case SPTK_EVENT_WINDOW_CLOSE:
            sptk_quit();
            break;
    }
}

int main()
{
    sptk_init("test", WIDTH, HEIGHT);
    sptk_window_set_handle(winhandle);
    
    winimg = sptk_window_get_image();
    
    blendimg = sptk_image32_create(WIDTH, HEIGHT);
    layerimg = sptk_image32_create(WIDTH, HEIGHT);
    
    sptk_image32_clear(layerimg, NULL);
    
    update_screen(NULL, -1);
    
    sptk_run();
    
    sptk_image32_free(blendimg);
    sptk_image32_free(layerimg);

    return 0;
}