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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - PNG textures with zero alpha channel have wrong rgb colors when reading them in a shader"
href="https://bugs.webkit.org/show_bug.cgi?id=165297">165297</a>
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<th>Summary</th>
<td>PNG textures with zero alpha channel have wrong rgb colors when reading them in a shader
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<th>Classification</th>
<td>Unclassified
</td>
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<th>Product</th>
<td>WebKit
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<th>Version</th>
<td>Safari 10
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<th>Hardware</th>
<td>iPhone / iPad
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<th>OS</th>
<td>iOS 10
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>Normal
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<th>Priority</th>
<td>P2
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<th>Component</th>
<td>WebGL
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<th>Assignee</th>
<td>webkit-unassigned@lists.webkit.org
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<th>Reporter</th>
<td>nederland074@gmail.com
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<th>CC</th>
<td>dino@apple.com
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<pre>Created <span class=""><a href="attachment.cgi?id=295932" name="attach_295932" title="Test archive (HTML + PNGs)">attachment 295932</a> <a href="attachment.cgi?id=295932&action=edit" title="Test archive (HTML + PNGs)">[details]</a></span>
Test archive (HTML + PNGs)
When reading a texture created from a PNG image in a shader (via the texture2D() call) the rgb color depends on the alpha value. If the alpha is zero, when the rgb color is completely black regardless of what's actually stored in texture channels. If the alpha is non-zero (even if it's 1/255) the rgb color is correct. This behavior makes it more difficult to use a texture as a storage for independent data in a form of packed together rgba channels.
This issue doesn't occur for a similar texture, that's created from a uint8array array buffer, so it's probably related to PNG images. Also, this issue doesn't occur in Safari/Chrome/Firefox under macOS 10.10.3.
In the attachment there is the example that demonstrates rendering the RGB color from a red texture which alpha channel filled with 1/255 value (working_image.png) and with zero value (not_working_image.png). Both should be red, but the latter is black on iPad.</pre>
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