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Code Issues Releases Wiki Activity

Check background/foreground luminance

This commit is contained in:
M66B 2021-08-04 08:10:39 +02:00
parent 65b63104fd
commit 4928d02dd3
1 changed files with 27 additions and 15 deletions
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42
app/src/main/java/eu/faircode/email/HtmlHelper.java
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@ -130,7 +130,7 @@ public class HtmlHelper {
private static final int DEFAULT_FONT_SIZE = 16; // pixels
private static final int DEFAULT_FONT_SIZE_PT = 12; // points
private static final int GRAY_THRESHOLD = Math.round(255 * 0.2f);
private static final double BG_LUM_THRESHOLD = 0.1;
private static final int COLOR_THRESHOLD = Math.round(255 * 0.1f);
private static final float MIN_LUMINANCE = 0.7f;
private static final int TAB_SIZE = 2;
private static final int MAX_ALT = 250;
@ -598,42 +598,46 @@ public class HtmlHelper {
Integer color = parseColor(value);
if ("color".equals(key)) {
boolean bg = false;
Integer bg = null;
if (background_color) {
Element e = element;
while (e != null && !bg)
while (e != null && bg == null)
if (e.hasAttr("x-background"))
bg = true;
bg = parseWebColor(e.attr("x-background"));
else
e = e.parent();
}
// Background color set:
// keep text color as-is
if (!bg) {
if (bg == null) {
// Special case:
// external draft / dark background / dark font
if (color != null && !view && dark) {
float lum = (float) ColorUtils.calculateLuminance(color);
if (lum < 0.1f)
double lum = ColorUtils.calculateLuminance(color);
if (lum < 0.1)
color = null;
}
if (color != null && view)
color = adjustColor(dark, textColorPrimary, color);
} else {
// Check background/foreground luminance
if (color != null) {
double lbg = ColorUtils.calculateLuminance(bg);
double lfg = ColorUtils.calculateLuminance(color);
if (Math.abs(lbg - lfg) < 0.1) {
color = (lbg < 0.5 ? Color.WHITE : Color.BLACK);
}
}
}
if (color != null)
element.attr("x-color", "true");
} else /* background */ {
if (color != null && view) {
double lum = ColorUtils.calculateLuminance(color);
if (dark ? lum < BG_LUM_THRESHOLD : lum > 1 - BG_LUM_THRESHOLD)
color = Color.TRANSPARENT;
}
if (color != null && !hasColor(color))
continue;
if (color != null)
element.attr("x-background", "true");
element.attr("x-background", encodeWebColor(color));
if (dark) {
boolean fg = false;
@ -1713,6 +1717,14 @@ public class HtmlHelper {
return color;
}
private static boolean hasColor(int color) {
int r = Color.red(color);
int g = Color.green(color);
int b = Color.blue(color);
return (Math.abs(r - g) >= COLOR_THRESHOLD ||
Math.abs(r - b) >= COLOR_THRESHOLD);
}
// https://tools.ietf.org/html/rfc3676
static String flow(String text) {
boolean continuation = false;