根据图像大小调整居中的文本字体大小。 如何？

Question

通过一些研究，我创建了以下代码来生成一个简单的图像，该图像的中心有一个文本字符串，显示该图像的分辨率。 挑战在于，当您将 X 和 Y 尺寸更改为更大或更小的值时，字体大小保持不变。

我的问题是，当用户在图像大小之间进行选择时，什么是“增大”或“缩小”字体大小的好方法？

我的一个想法是计算预定区域，将它们添加到键值对数组中，其中值是给定区域范围的硬编码字体大小。

也许你有一个更简单的想法？

PS：我使用的字体可以从 Google fonts 下载：

蒙特塞拉特-半粗体

output 看起来像这样：

和代码：

<?php

  // We Declare our canvas width & height dimensions
  $myCanvasWidth  = 256;
  $myCanvasHeight = 256;

  // We Create an empty and dark canvas from these dimensions above
  $myCanvas = imagecreate($myCanvasWidth, $myCanvasHeight) or die("Can't create image!");
  // We Allocate a color to be used as the canvas background
  $colorIndigo = imagecolorallocate($myCanvas, 0x3F, 0x51, 0xB5);
  // We Apply color as canvas background
  imagefill($myCanvas, 0, 0, $colorIndigo);

  // We Allocate a color to be used with the canvas text
  $colorWhite = imagecolorallocate($myCanvas, 0xFF, 0xFF, 0xFF);

  // We Declare our TTF font path in Windows 10...
  $myFont = 'J:\Montserrat-SemiBold.ttf';
  // We set the font size
  $myFontSize = 16;
  // We set the text angle
  $myTextAngle = 0;

  // We Declare the text string to be drawn on canvas...
  $myText = $myCanvasWidth . ' x ' . $myCanvasHeight;

  // We Calculate and return the bounding box in pixels for the text string to be drawn on canvas...
  $myTextBoundingBox = imageftbbox($myFontSize, $myTextAngle, $myFont, $myText);

  // Get the text upper, lower, left and right corner bounds of our text bounding box...
  $lower_left_x  = $myTextBoundingBox[0]; 
  $lower_left_y  = $myTextBoundingBox[1];
  $lower_right_x = $myTextBoundingBox[2];
  $lower_right_y = $myTextBoundingBox[3];
  $upper_right_x = $myTextBoundingBox[4];
  $upper_right_y = $myTextBoundingBox[5];
  $upper_left_x  = $myTextBoundingBox[6];
  $upper_left_y  = $myTextBoundingBox[7];

  // Get Text Width and Height
  $myTextWidth  =  $lower_right_x - $lower_left_x; //or  $upper_right_x - $upper_left_x
  $myTextHeight = $lower_right_y - $upper_right_y; //or  $lower_left_y - $upper_left_y

  //Get the starting position for centering
  $start_x_offset = ($myCanvasWidth - $myTextWidth) / 2;
  $start_y_offset = (($myCanvasHeight - $myTextHeight) + $myFontSize * 2) / 2;

  // Write text to the image using TrueType fonts
  imagettftext($myCanvas, $myFontSize, $myTextAngle, $start_x_offset, $start_y_offset, $colorWhite, $myFont, $myText);

  // Draw a horizontal dashed line for reference only
  imagedashedline($myCanvas, 0, $myCanvasHeight/2, $myCanvasWidth, $myCanvasHeight/2, $colorWhite);
  // Draw a vertical dashed line for reference only
  imagedashedline($myCanvas, $myCanvasWidth/2, 0, $myCanvasWidth/2, $myCanvasHeight, $colorWhite);

  // We se the correct http header for png images...
  header('Content-Type: image/png');

  // We Output a PNG image to either the browser or a file
  imagepng($myCanvas);
  // Free any memory associated with myCanvas; image. 
  imagedestroy($myCanvas);

?>

Answer 1

这是上面作为答案实施的评论。 有趣的是，即使线条和字体看起来没有对齐，它们实际上是居中的。

中心的“x”会产生不对齐的错觉； 不使用等间距 fonts 的可能副作用是为了实现更不必要的精确 alignment..？！

再说一次.. 等距的 fonts 不是那么好看...

示例调整大小输出：

<?php

  // We Declare our canvas width & height dimensions
  $myCanvasWidth  = 640;
  $myCanvasHeight = 360;

  // We Create an empty and dark canvas from these dimensions above
  $myCanvas = imagecreate($myCanvasWidth, $myCanvasHeight) or die("Can't create image!");
  // We Allocate a color to be used as the canvas background
  $colorIndigo = imagecolorallocate($myCanvas, 0x3F, 0x51, 0xB5);
  // We Apply color as canvas background
  imagefill($myCanvas, 0, 0, $colorIndigo);

  // We Allocate a color to be used with the canvas text
  $colorWhite = imagecolorallocate($myCanvas, 0xFF, 0xFF, 0xFF);

  // We Declare our TTF font path in Windows 10...
  $myFont = 'J:\Montserrat-SemiBold.ttf';

  // Static font seed value...
  $fontSize = 16;
  // We set the dynamic font size
  $myFontSize = $myCanvasWidth / $fontSize;
  // We set the text angle
  $myTextAngle = 0;

  // We Declare the text string to be drawn on canvas...
  $myText = $myCanvasWidth . ' x ' . $myCanvasHeight;

  // We Calculate and return the bounding box in pixels for the text string to be drawn on canvas...
  $myTextBoundingBox = imageftbbox($myFontSize, $myTextAngle, $myFont, $myText);

  // Get the text upper, lower, left and right corner bounds of our text bounding box...
  $lower_left_x  = $myTextBoundingBox[0]; 
  $lower_left_y  = $myTextBoundingBox[1];
  $lower_right_x = $myTextBoundingBox[2];
  $lower_right_y = $myTextBoundingBox[3];
  $upper_right_x = $myTextBoundingBox[4];
  $upper_right_y = $myTextBoundingBox[5];
  $upper_left_x  = $myTextBoundingBox[6];
  $upper_left_y  = $myTextBoundingBox[7];

  // Get Text Width and Height
  $myTextWidth  =  $lower_right_x - $lower_left_x; //or  $upper_right_x - $upper_left_x
  $myTextHeight = $lower_right_y - $upper_right_y; //or  $lower_left_y - $upper_left_y

  //Get the starting position for centering
  $start_x_offset = ($myCanvasWidth - $myTextWidth) / 2;
  $start_y_offset = (($myCanvasHeight - $myTextHeight) + $myFontSize * 2) / 2;

  // Write text to the image using TrueType fonts
  imagettftext($myCanvas, $myFontSize, $myTextAngle, $start_x_offset, $start_y_offset, $colorWhite, $myFont, $myText);

  // Draw a horizontal dashed line for reference only
  imagedashedline($myCanvas, 0, $myCanvasHeight/2, $myCanvasWidth, $myCanvasHeight/2, $colorWhite);
  // Draw a vertical dashed line for reference only
  imagedashedline($myCanvas, $myCanvasWidth/2, 0, $myCanvasWidth/2, $myCanvasHeight, $colorWhite);

  // We set the correct http header for png images...
  header('Content-Type: image/png');

  // We Output a PNG image to either the browser or a file
  imagepng($myCanvas);
  // Finally, we free any memory associated with myCanvas; the image. 
  imagedestroy($myCanvas);

?>

图示的imageftbbox() function。

imageftbbox()返回一个包含 8 个元素的数组，这些元素代表构成文本边界框的四个点：