2D screenpace zooming

Question

我需要在perl上绘制2D图像到大小为1024x768的图像;行的坐标是unix时间戳，如x1 = 1365693813 y1 =（某个虚拟中心）x2 = 1365793815 y2 =（某个虚拟中心）。什么公式可以将真实生活中的图像缩放到图像空间中？

Answer 1

假设($x1,$y1)和($x2,$y2)定义“视图窗口”你的左下角和右上角的角落，你有一个点要绘制($x3,$y3)其中$x1 <= $x3 <= $x2和$y1 <= $y3 <= $y2。另外假设您正在标准图像空间中（0,0）是图像的左上角。你可以找到($xp, $yp)为像素坐标，以这样的图像绘制：

# View window 
my ($x1,$y1) = (1365693813, 100); 
my ($x2,$y2) = (1365693815, 200); 
my ($vw ,$vh) = ($x2 - $1, $y2 - $y1); 

# Image width/height 
my ($imgw,$imgh) = (1024, 768); 

# Point to plot in original co-ordinates 
my ($x3,$y3) = (1365693814, 150); 

# Calculate point to plot in image co-ordinates 
my $xp = int(($imgw * ($x3 - $x1)/$vw) + 0.5); 
my $yp = int(($imgh * (1.0 - ($y3 - $y1)/$vh)) + 0.5); 

# Now plot ($xp, $yp), provided it is inside the graphic!