[a11y] Lower threshold for non-stopword image alt text to 3 characters
This commit lowers the threshold for image alt text from 4 to 3 characters, but only for alt text that is not composed primarily of stop words. This means that images with alt text that is 3 characters or longer and contains non-stop words will no longer be considered for automatic image descriptions. This change is being made in response to user feedback that the previous threshold was too high and was preventing some images with useful alt text from being described. Because this change only affects alt text containing non-stop words, its impact is expected to be low. Alternatives considered: * Removing the threshold altogether. This was rejected because it could lead to generating image descriptions for images where they are not needed, potentially creating a confusing experience for users. * Modifying the screen reader hint to provide different guidance when: * An image has no alt text at all (suggesting the use of the context menu to get a description). * An image has some alt text present (suggesting the use of the context menu for expanded image descriptions). The following histograms will be used to track the impact of this change: * Accessibility.ImageAnnotation.ServerRequests * Accessibility.ImageAnnotation.CacheHits If we see a significant decrease in the number of server requests or cache hits, we may need to revisit this change. Bug: 389897606 Change-Id: Ife64a1bfd7cd1be06c174a02338ec7e9065a1b6d Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6191348 Reviewed-by: Mark Schillaci <mschillaci@google.com> Reviewed-by: Aaron Leventhal <aleventhal@chromium.org> Reviewed-by: David Tseng <dtseng@chromium.org> Commit-Queue: Lucas Radaelli <lucasradaelli@google.com> Cr-Commit-Position: refs/heads/main@{#1425794}
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Chromium LUCI CQ

parent
e04a4524b7
commit
329749f3fc
content
browser
accessibility
renderer
accessibility
annotations
test
@ -4100,6 +4100,10 @@ IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilityNestedList) {
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RunHtmlTest(FILE_PATH_LITERAL("nestedlist.html"));
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}
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IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest, AccessibilitySmallAlt) {
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RunHtmlTest(FILE_PATH_LITERAL("small-alt.html"));
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}
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IN_PROC_BROWSER_TEST_P(DumpAccessibilityTreeTest,
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AccessibilityNextAndPreviousOnLineId) {
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RunHtmlTest(FILE_PATH_LITERAL("next-and-previous-on-line-id.html"));
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@ -607,12 +607,12 @@ bool AXImageAnnotator::ImageNameHasMostlyStopwords(
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// Compute how many characters remain after removing stopwords.
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int remaining_codepoints = GetLengthAfterRemovingStopwords(image_name);
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// If there are 3 or fewer unicode codepoints remaining, classify
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// If there are less than 3 unicode codepoints remaining, classify
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// the string as "mostly stopwords".
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//
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// More details and analysis in this (Google-internal) design doc:
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// http://goto.google.com/augment-existing-image-descriptions
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return (remaining_codepoints <= 3);
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return (remaining_codepoints < 3);
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}
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#if defined(CONTENT_IMPLEMENTATION)
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@ -5066,6 +5066,8 @@ data/accessibility/html/simple_spans.html
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data/accessibility/html/slot-display-contents-expected-auralinux.txt
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data/accessibility/html/slot-display-contents-expected-blink.txt
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data/accessibility/html/slot-display-contents.html
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data/accessibility/html/small-alt-expected-blink.txt
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data/accessibility/html/small-alt.html
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data/accessibility/html/small-expected-android-assist-data.txt
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data/accessibility/html/small-expected-android-external.txt
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data/accessibility/html/small-expected-android.txt
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@ -0,0 +1,7 @@
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rootWebArea name='Robert Downey Jr.'
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++genericContainer ignored
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++++genericContainer
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++++++image name='Bob' imageAnnotationStatus=ineligibleForAnnotation
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++++++staticText name=' '
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++++++++inlineTextBox name=' '
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++++++image name='Robert' imageAnnotationStatus=ineligibleForAnnotation
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content/test/data/accessibility/html/small-alt.html
Normal file
23
content/test/data/accessibility/html/small-alt.html
Normal file
@ -0,0 +1,23 @@
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<!--
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@BLINK-ALLOW:imageAnnotation*
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@BLINK_ALLOW:name=*
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-->
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Robert Downey Jr.</title>
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</head>
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<body>
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<img
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alt="Bob"
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src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Robert_Downey_Jr._2014_Comic-Con.jpg/1024px-Robert_Downey_Jr._2014_Comic-Con.jpg">
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<img
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alt="Robert"
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src="https://upload.wikimedia.org/wikipedia/commons/thumb/2/23/Robert_Downey_Jr._2014_Comic-Con.jpg/1024px-Robert_Downey_Jr._2014_Comic-Con.jpg">
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</body>
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</html>
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