Add a CSS corner if the contrast between QR margin and page background is too low

2 months ago · 2a6a4ad056
3 changed files with 62 additions and 9 deletions
--- a/index.php
+++ b/index.php
@ -76,6 +76,8 @@ if (
    require_once "less.php/lib/Less/Autoloader.php";
    Less_Autoloader::register();

+    $colorScheme['theme'] = $theme;
+
    $options = array('cache_dir' => 'css/', 'compress' => true);
    $cssFileName = Less_Cache::Get(array("style.less" => ""), $options, $colorScheme);
    ?>
@ -194,6 +196,12 @@ if (

      if (!empty($params['txt'])) {

+        $rgbBgColor = array(
+          'r' => hexdec(substr($params['bgColor'],0,2)),
+          'g' => hexdec(substr($params['bgColor'],2,2)),
+          'b' => hexdec(substr($params['bgColor'],4,2)),
+        );
+
        require "barcode-generator/Utils/QrCode.php";
        $qrCode = new QrCode();
        if (!is_null($params['margin']))
@ -207,11 +215,7 @@ if (
            'g' => hexdec(substr($params['mainColor'],2,2)),
            'b' => hexdec(substr($params['mainColor'],4,2)),
          ))
-          ->setBackgroundColor(array(
-            'r' => hexdec(substr($params['bgColor'],0,2)),
-            'g' => hexdec(substr($params['bgColor'],2,2)),
-            'b' => hexdec(substr($params['bgColor'],4,2)),
-          ))
+          ->setBackgroundColor($rgbBgColor)
          ->setImageType(QrCode::IMAGE_TYPE_PNG);
        $dataUri = $qrCode->getDataUri();
        $qrSize = $qrCode->getSize() + 2 * $qrCode->getPadding();
@ -224,7 +228,19 @@ if (
          </div>

          <div class="centered" id="showOnlyQR">
-            <a title="<?= $loc['title_showOnlyQR'] ?>" href="<?= $dataUri ?>"><img width="<?= $qrSize ?>" height="<?= $qrSize ?>" alt='<?= $loc['alt_QR_before'] ?><?= htmlspecialchars($params['txt']); ?><?= $loc['alt_QR_after'] ?>' id="qrCode" src="<?= $dataUri ?>"></a>
+            <a title="<?= $loc['title_showOnlyQR'] ?>" href="<?= $dataUri ?>"><img width="<?= $qrSize ?>" height="<?= $qrSize ?>" alt='<?= $loc['alt_QR_before'] ?><?= htmlspecialchars($params['txt']); ?><?= $loc['alt_QR_after'] ?>' id="qrCode"<?php
+
+              // Compute the difference between the QR code and theme background colors
+              $diffLight = abs($rgbBgColor['r']-hexdec(substr($colorScheme['bg-light'],-6,2))) + abs($rgbBgColor['g']-hexdec(substr($colorScheme['bg-light'],-4,2))) + abs($rgbBgColor['b']-hexdec(substr($colorScheme['bg-light'],-2,2)));
+              $diffDark = abs($rgbBgColor['r']-hexdec(substr($colorScheme['bg-dark'],-6,2))) + abs($rgbBgColor['g']-hexdec(substr($colorScheme['bg-dark'],-4,2))) + abs($rgbBgColor['b']-hexdec(substr($colorScheme['bg-dark'],-2,2)));
+
+              // Determine whether a CSS corner is needed to let the user see the margin of the QR code
+              $contrastThreshold = 64;
+              if ($diffLight < $contrastThreshold)
+                echo " class='needLightContrast'";
+              if ($diffDark < $contrastThreshold)
+                echo " class='needDarkContrast'";
+              ?> src="<?= $dataUri ?>"></a>
          </div>
        </section>

--- a/style.less
+++ b/style.less
@ -104,6 +104,41 @@ a {

 #qrCode {
  max-width: 480px;
+  @width: 2px;
+  @lenght: 16px;
+  padding: @width;
+
+  &.needLightContrast {
+    @media @light {
+      background:
+        linear-gradient(to right, @borderQr-light @width, transparent 0px) 0 0,
+        linear-gradient(to right, @borderQr-light @width, transparent 0px) 0 100%,
+        linear-gradient(to left, @borderQr-light @width, transparent 0px) 100% 0,
+        linear-gradient(to left, @borderQr-light @width, transparent 0px) 100% 100%,
+        linear-gradient(to bottom, @borderQr-light @width, transparent 0px) 0 0,
+        linear-gradient(to bottom, @borderQr-light @width, transparent 0px) 100% 0,
+        linear-gradient(to top, @borderQr-light @width, transparent 0px) 0 100%,
+        linear-gradient(to top, @borderQr-light @width, transparent 0px) 100% 100%;
+      background-repeat: no-repeat;
+      background-size: @lenght @lenght;
+    }
+  }
+
+  &.needDarkContrast {
+    @media @dark {
+      background:
+        linear-gradient(to right, @borderQr-dark @width, transparent 0px) 0 0,
+        linear-gradient(to right, @borderQr-dark @width, transparent 0px) 0 100%,
+        linear-gradient(to left, @borderQr-dark @width, transparent 0px) 100% 0,
+        linear-gradient(to left, @borderQr-dark @width, transparent 0px) 100% 100%,
+        linear-gradient(to bottom, @borderQr-dark @width, transparent 0px) 0 0,
+        linear-gradient(to bottom, @borderQr-dark @width, transparent 0px) 100% 0,
+        linear-gradient(to top, @borderQr-dark @width, transparent 0px) 0 100%,
+        linear-gradient(to top, @borderQr-dark @width, transparent 0px) 100% 100%;
+      background-repeat: no-repeat;
+      background-size: @lenght @lenght;
+    }
+  }
 }

 .centered {
--- a/themes/libreqr/theme.php
+++ b/themes/libreqr/theme.php
@ -6,7 +6,7 @@ $themeDimensionsIcons = array(16, 32, 48, 64, 96, 128, 192, 256, 384, 512);
 $colorScheme = array(
  // Light theme
  "text-light" => "#2a2a2a",
-  "bg-light" => "white",
+  "bg-light" => "#ffffff", // Must be a long hexadecimal color
  "bgField-light" => "#eeeeee",
  "bgHelp-light" => "#ececec",
  "bgTextarea-light" => "#e5e5e5",
@ -15,9 +15,10 @@ $colorScheme = array(
  "border-light" => "#65666b",
  "borderHover-light" => "#46484e",
  "borderFocus-light" => "#2a2a2a",
+  "borderQr-light" => "gray",
  // Dark theme
  "text-dark" => "white",
-  "bg-dark" => "#2a2a2a",
+  "bg-dark" => "#2a2a2a", // Must be a long hexadecimal color
  "bgField-dark" => "#31363B",
  "bgHelp-dark" => "#151616",
  "bgTextarea-dark" => "#232629",
@ -25,5 +26,6 @@ $colorScheme = array(
  "textareaPlaceholder-dark" => "#bababa",
  "border-dark" => "#5f5f5f",
  "borderHover-dark" => "#808080",
-  "borderFocus-dark" => "white"
+  "borderFocus-dark" => "white",
+  "borderQr-dark" => "gray",
 );