在PHP中计算沿对角线y = x的距离 [英] Calculating distance along a diagonal y=x in PHP

问题描述

想象一下，我有一个从左下角到右上角有一条对角线的正方形。给定任意点（x，y），我希望能够确定该点在该线上的距离。这是因为我想创建从一种颜色到另一种颜色的颜色渐变，从正方形的左下角到右上角。



此图像显示我的工作这里;



给定任意点（90,50），我相信我应该计算形成的三角形的斜边沿着正方形的斜边开始。该点是直接对角线，因此它沿着正方形的斜边映射到位置z。



因此我应该能够执行以下操作来生成RGB值：

Hi,

Imagine I have a square with a diagonal line from the bottom left to the top right corner. Given any point (x,y), I want to be able to determine how far along that line the point is. This is because I want to create a colour gradient from one colour to another, from bottom left to top right of a square.

This image displays my working here;

Given the arbitrary point (90,50), I believe I should calculate where the hypotenuse of the formed triangle begins along the square's hypotenuse. The point is directly diagonal, so it maps to position z along the square's hypotenuse.

Therefore I should be able to do the following to generate an RGB value:

$r = self::map(hypot($y, $y) + (hypot($x, $y) / 2), 0, hypot($imgW, $imgH), 0, 255);
$c = ImageColorAllocate($base_image, 0, $r, $r);

从0到斜边长度映射到0-255。



任何人都可以帮我弄清楚为什么输出是这里 [ ^ ]？



有两个问题;渐变是完全错误的，右下方有一些黑色像素似乎选择不参与此代码。



我尝试过的：



----------------------------- -----------------------

by mapping from 0 to the hypotenuse length, to 0-255.

Could anyone please help me to figure out why the output is this here[^]?

There are two issues; the gradient is completely wrong, and there are some black pixels in the bottom right which have seemingly chosen not to participate in this code.

What I have tried:

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推荐答案

r = self :: map（hypot（

r = self::map(hypot(

y，

y）+（hypot（

y) + (hypot(

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