<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source to the Rust file `/home/mrh/.cargo/registry/src/github.com-1ecc6299db9ec823/image-0.21.2/./src/ico/decoder.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>decoder.rs.html -- source</title><link rel="stylesheet" type="text/css" href="../../../normalize.css"><link rel="stylesheet" type="text/css" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" type="text/css" href="../../../dark.css"><link rel="stylesheet" type="text/css" href="../../../light.css" id="themeStyle"><script src="../../../storage.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="shortcut icon" href="../../../favicon.ico"><style type="text/css">#crate-search{background-image:url("../../../down-arrow.svg");}</style></head><body class="rustdoc source"><!--[if lte IE 8]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><div class="sidebar-menu">☰</div><a href='../../../image/index.html'><div class='logo-container'><img src='../../../rust-logo.png' alt='logo'></div></a></nav><div class="theme-picker"><button id="theme-picker" aria-label="Pick another theme!"><img src="../../../brush.svg" width="18" alt="Pick another theme!"></button><div id="theme-choices"></div></div><script src="../../../theme.js"></script><nav class="sub"><form class="search-form js-only"><div class="search-container"><div><select id="crate-search"><option value="All crates">All crates</option></select><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"></div><a id="settings-menu" href="../../../settings.html"><img src="../../../wheel.svg" width="18" alt="Change settings"></a></div></form></nav><section id="main" class="content"><pre class="line-numbers"><span id="1"> 1</span>
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</pre><div class="example-wrap"><pre class="rust ">
<span class="kw">use</span> <span class="ident">byteorder</span>::{<span class="ident">LittleEndian</span>, <span class="ident">ReadBytesExt</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">io</span>::{<span class="ident">Cursor</span>, <span class="ident">Read</span>, <span class="ident">Seek</span>, <span class="ident">SeekFrom</span>};
<span class="kw">use</span> <span class="ident">color</span>::<span class="ident">ColorType</span>;
<span class="kw">use</span> <span class="ident">image</span>::{<span class="ident">ImageDecoder</span>, <span class="ident">ImageError</span>, <span class="ident">ImageResult</span>};
<span class="kw">use</span> <span class="self">self</span>::<span class="ident">InnerDecoder</span>::<span class="kw-2">*</span>;
<span class="kw">use</span> <span class="ident">bmp</span>::<span class="ident">BMPDecoder</span>;
<span class="kw">use</span> <span class="ident">png</span>::<span class="ident">PNGDecoder</span>;
<span class="comment">// http://www.w3.org/TR/PNG-Structure.html</span>
<span class="comment">// The first eight bytes of a PNG file always contain the following (decimal) values:</span>
<span class="kw">const</span> <span class="ident">PNG_SIGNATURE</span>: [<span class="ident">u8</span>; <span class="number">8</span>] <span class="op">=</span> [<span class="number">137</span>, <span class="number">80</span>, <span class="number">78</span>, <span class="number">71</span>, <span class="number">13</span>, <span class="number">10</span>, <span class="number">26</span>, <span class="number">10</span>];
<span class="doccomment">/// An ico decoder</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">ICODecoder</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span><span class="op">></span> {
<span class="ident">selected_entry</span>: <span class="ident">DirEntry</span>,
<span class="ident">inner_decoder</span>: <span class="ident">InnerDecoder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span>,
}
<span class="kw">enum</span> <span class="ident">InnerDecoder</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span><span class="op">></span> {
<span class="ident">BMP</span>(<span class="ident">BMPDecoder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span>),
<span class="ident">PNG</span>(<span class="ident">PNGDecoder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span>),
}
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">Default</span>)]</span>
<span class="kw">struct</span> <span class="ident">DirEntry</span> {
<span class="ident">width</span>: <span class="ident">u8</span>,
<span class="ident">height</span>: <span class="ident">u8</span>,
<span class="ident">color_count</span>: <span class="ident">u8</span>,
<span class="ident">reserved</span>: <span class="ident">u8</span>,
<span class="ident">num_color_planes</span>: <span class="ident">u16</span>,
<span class="ident">bits_per_pixel</span>: <span class="ident">u16</span>,
<span class="ident">image_length</span>: <span class="ident">u32</span>,
<span class="ident">image_offset</span>: <span class="ident">u32</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span> <span class="op">+</span> <span class="ident">Seek</span><span class="op">></span> <span class="ident">ICODecoder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> {
<span class="doccomment">/// Create a new decoder that decodes from the stream ```r```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="kw-2">mut</span> <span class="ident">r</span>: <span class="ident">R</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span><span class="ident">ICODecoder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">entries</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">read_entries</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">r</span>));
<span class="kw">let</span> <span class="ident">entry</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">best_entry</span>(<span class="ident">entries</span>));
<span class="kw">let</span> <span class="ident">decoder</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">entry</span>.<span class="ident">decoder</span>(<span class="ident">r</span>));
<span class="prelude-val">Ok</span>(<span class="ident">ICODecoder</span> {
<span class="ident">selected_entry</span>: <span class="ident">entry</span>,
<span class="ident">inner_decoder</span>: <span class="ident">decoder</span>,
})
}
}
<span class="kw">fn</span> <span class="ident">read_entries</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span><span class="op">></span>(<span class="ident">r</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">R</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">DirEntry</span><span class="op">></span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">_reserved</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u16</span>::<span class="op"><</span><span class="ident">LittleEndian</span><span class="op">></span>());
<span class="kw">let</span> <span class="ident">_type</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u16</span>::<span class="op"><</span><span class="ident">LittleEndian</span><span class="op">></span>());
<span class="kw">let</span> <span class="ident">count</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u16</span>::<span class="op"><</span><span class="ident">LittleEndian</span><span class="op">></span>());
(<span class="number">0</span>..<span class="ident">count</span>).<span class="ident">map</span>(<span class="op">|</span><span class="kw">_</span><span class="op">|</span> <span class="ident">read_entry</span>(<span class="ident">r</span>)).<span class="ident">collect</span>()
}
<span class="kw">fn</span> <span class="ident">read_entry</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span><span class="op">></span>(<span class="ident">r</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">R</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span><span class="ident">DirEntry</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">entry</span> <span class="op">=</span> <span class="ident">DirEntry</span>::<span class="ident">default</span>();
<span class="ident">entry</span>.<span class="ident">width</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u8</span>());
<span class="ident">entry</span>.<span class="ident">height</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u8</span>());
<span class="ident">entry</span>.<span class="ident">color_count</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u8</span>());
<span class="comment">// Reserved value (not used)</span>
<span class="ident">entry</span>.<span class="ident">reserved</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u8</span>());
<span class="comment">// This may be either the number of color planes (0 or 1), or the horizontal coordinate</span>
<span class="comment">// of the hotspot for CUR files.</span>
<span class="ident">entry</span>.<span class="ident">num_color_planes</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u16</span>::<span class="op"><</span><span class="ident">LittleEndian</span><span class="op">></span>());
<span class="kw">if</span> <span class="ident">entry</span>.<span class="ident">num_color_planes</span> <span class="op">></span> <span class="number">256</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">ImageError</span>::<span class="ident">FormatError</span>(
<span class="string">"ICO image entry has a too large color planes/hotspot value"</span>.<span class="ident">to_string</span>(),
));
}
<span class="comment">// This may be either the bit depth (may be 0 meaning unspecified),</span>
<span class="comment">// or the vertical coordinate of the hotspot for CUR files.</span>
<span class="ident">entry</span>.<span class="ident">bits_per_pixel</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u16</span>::<span class="op"><</span><span class="ident">LittleEndian</span><span class="op">></span>());
<span class="kw">if</span> <span class="ident">entry</span>.<span class="ident">bits_per_pixel</span> <span class="op">></span> <span class="number">256</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">ImageError</span>::<span class="ident">FormatError</span>(
<span class="string">"ICO image entry has a too large bits per pixel/hotspot value"</span>.<span class="ident">to_string</span>(),
));
}
<span class="ident">entry</span>.<span class="ident">image_length</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u32</span>::<span class="op"><</span><span class="ident">LittleEndian</span><span class="op">></span>());
<span class="ident">entry</span>.<span class="ident">image_offset</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u32</span>::<span class="op"><</span><span class="ident">LittleEndian</span><span class="op">></span>());
<span class="prelude-val">Ok</span>(<span class="ident">entry</span>)
}
<span class="doccomment">/// Find the entry with the highest (color depth, size).</span>
<span class="kw">fn</span> <span class="ident">best_entry</span>(<span class="kw-2">mut</span> <span class="ident">entries</span>: <span class="ident">Vec</span><span class="op"><</span><span class="ident">DirEntry</span><span class="op">></span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span><span class="ident">DirEntry</span><span class="op">></span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">best</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">entries</span>.<span class="ident">pop</span>().<span class="ident">ok_or</span>(<span class="ident">ImageError</span>::<span class="ident">ImageEnd</span>));
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">best_score</span> <span class="op">=</span> (
<span class="ident">best</span>.<span class="ident">bits_per_pixel</span>,
<span class="ident">u32</span>::<span class="ident">from</span>(<span class="ident">best</span>.<span class="ident">real_width</span>()) <span class="op">*</span> <span class="ident">u32</span>::<span class="ident">from</span>(<span class="ident">best</span>.<span class="ident">real_height</span>()),
);
<span class="kw">for</span> <span class="ident">entry</span> <span class="kw">in</span> <span class="ident">entries</span> {
<span class="kw">let</span> <span class="ident">score</span> <span class="op">=</span> (
<span class="ident">entry</span>.<span class="ident">bits_per_pixel</span>,
<span class="ident">u32</span>::<span class="ident">from</span>(<span class="ident">entry</span>.<span class="ident">real_width</span>()) <span class="op">*</span> <span class="ident">u32</span>::<span class="ident">from</span>(<span class="ident">entry</span>.<span class="ident">real_height</span>()),
);
<span class="kw">if</span> <span class="ident">score</span> <span class="op">></span> <span class="ident">best_score</span> {
<span class="ident">best</span> <span class="op">=</span> <span class="ident">entry</span>;
<span class="ident">best_score</span> <span class="op">=</span> <span class="ident">score</span>;
}
}
<span class="prelude-val">Ok</span>(<span class="ident">best</span>)
}
<span class="kw">impl</span> <span class="ident">DirEntry</span> {
<span class="kw">fn</span> <span class="ident">real_width</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">u16</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">width</span> {
<span class="number">0</span> <span class="op">=</span><span class="op">></span> <span class="number">256</span>,
<span class="ident">w</span> <span class="op">=</span><span class="op">></span> <span class="ident">u16</span>::<span class="ident">from</span>(<span class="ident">w</span>),
}
}
<span class="kw">fn</span> <span class="ident">real_height</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">u16</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">height</span> {
<span class="number">0</span> <span class="op">=</span><span class="op">></span> <span class="number">256</span>,
<span class="ident">h</span> <span class="op">=</span><span class="op">></span> <span class="ident">u16</span>::<span class="ident">from</span>(<span class="ident">h</span>),
}
}
<span class="kw">fn</span> <span class="ident">matches_dimensions</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">width</span>: <span class="ident">u64</span>, <span class="ident">height</span>: <span class="ident">u64</span>) <span class="op">-</span><span class="op">></span> <span class="ident">bool</span> {
<span class="ident">u64</span>::<span class="ident">from</span>(<span class="self">self</span>.<span class="ident">real_width</span>()) <span class="op">=</span><span class="op">=</span> <span class="ident">width</span> <span class="kw-2">&</span><span class="op">&</span> <span class="ident">u64</span>::<span class="ident">from</span>(<span class="self">self</span>.<span class="ident">real_height</span>()) <span class="op">=</span><span class="op">=</span> <span class="ident">height</span>
}
<span class="kw">fn</span> <span class="ident">seek_to_start</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span> <span class="op">+</span> <span class="ident">Seek</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">r</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">R</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span>()<span class="op">></span> {
<span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">seek</span>(<span class="ident">SeekFrom</span>::<span class="ident">Start</span>(<span class="ident">u64</span>::<span class="ident">from</span>(<span class="self">self</span>.<span class="ident">image_offset</span>))));
<span class="prelude-val">Ok</span>(())
}
<span class="kw">fn</span> <span class="ident">is_png</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span> <span class="op">+</span> <span class="ident">Seek</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">r</span>: <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">R</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span><span class="ident">bool</span><span class="op">></span> {
<span class="macro">try</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">seek_to_start</span>(<span class="ident">r</span>));
<span class="comment">// Read the first 8 bytes to sniff the image.</span>
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">signature</span> <span class="op">=</span> [<span class="number">0u8</span>; <span class="number">8</span>];
<span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_exact</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">signature</span>));
<span class="prelude-val">Ok</span>(<span class="ident">signature</span> <span class="op">=</span><span class="op">=</span> <span class="ident">PNG_SIGNATURE</span>)
}
<span class="kw">fn</span> <span class="ident">decoder</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span> <span class="op">+</span> <span class="ident">Seek</span><span class="op">></span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="kw-2">mut</span> <span class="ident">r</span>: <span class="ident">R</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span><span class="ident">InnerDecoder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span><span class="op">></span> {
<span class="kw">let</span> <span class="ident">is_png</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">is_png</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">r</span>));
<span class="macro">try</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">seek_to_start</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">r</span>));
<span class="kw">if</span> <span class="ident">is_png</span> {
<span class="prelude-val">Ok</span>(<span class="ident">PNG</span>(<span class="ident">PNGDecoder</span>::<span class="ident">new</span>(<span class="ident">r</span>)<span class="question-mark">?</span>))
} <span class="kw">else</span> {
<span class="prelude-val">Ok</span>(<span class="ident">BMP</span>(<span class="ident">BMPDecoder</span>::<span class="ident">new_with_ico_format</span>(<span class="ident">r</span>)<span class="question-mark">?</span>))
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">R</span>: <span class="ident">Read</span> <span class="op">+</span> <span class="ident">Seek</span><span class="op">></span> <span class="ident">ImageDecoder</span> <span class="kw">for</span> <span class="ident">ICODecoder</span><span class="op"><</span><span class="ident">R</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">Reader</span> <span class="op">=</span> <span class="ident">Cursor</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span><span class="op">></span>;
<span class="kw">fn</span> <span class="ident">dimensions</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> (<span class="ident">u64</span>, <span class="ident">u64</span>) {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">inner_decoder</span> {
<span class="ident">BMP</span>(<span class="kw-2">ref</span> <span class="ident">decoder</span>) <span class="op">=</span><span class="op">></span> <span class="ident">decoder</span>.<span class="ident">dimensions</span>(),
<span class="ident">PNG</span>(<span class="kw-2">ref</span> <span class="ident">decoder</span>) <span class="op">=</span><span class="op">></span> <span class="ident">decoder</span>.<span class="ident">dimensions</span>(),
}
}
<span class="kw">fn</span> <span class="ident">colortype</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ColorType</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">inner_decoder</span> {
<span class="ident">BMP</span>(<span class="kw-2">ref</span> <span class="ident">decoder</span>) <span class="op">=</span><span class="op">></span> <span class="ident">decoder</span>.<span class="ident">colortype</span>(),
<span class="ident">PNG</span>(<span class="kw-2">ref</span> <span class="ident">decoder</span>) <span class="op">=</span><span class="op">></span> <span class="ident">decoder</span>.<span class="ident">colortype</span>(),
}
}
<span class="kw">fn</span> <span class="ident">into_reader</span>(<span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">Reader</span><span class="op">></span> {
<span class="prelude-val">Ok</span>(<span class="ident">Cursor</span>::<span class="ident">new</span>(<span class="self">self</span>.<span class="ident">read_image</span>()<span class="question-mark">?</span>))
}
<span class="kw">fn</span> <span class="ident">read_image</span>(<span class="self">self</span>) <span class="op">-</span><span class="op">></span> <span class="ident">ImageResult</span><span class="op"><</span><span class="ident">Vec</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span><span class="op">></span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">inner_decoder</span> {
<span class="ident">PNG</span>(<span class="ident">decoder</span>) <span class="op">=</span><span class="op">></span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">selected_entry</span>.<span class="ident">image_length</span> <span class="op"><</span> <span class="ident">PNG_SIGNATURE</span>.<span class="ident">len</span>() <span class="kw">as</span> <span class="ident">u32</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">ImageError</span>::<span class="ident">FormatError</span>(
<span class="string">"Entry specified a length that is shorter than PNG header!"</span>.<span class="ident">to_string</span>(),
));
}
<span class="comment">// Check if the image dimensions match the ones in the image data.</span>
<span class="kw">let</span> (<span class="ident">width</span>, <span class="ident">height</span>) <span class="op">=</span> <span class="ident">decoder</span>.<span class="ident">dimensions</span>();
<span class="kw">if</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">selected_entry</span>.<span class="ident">matches_dimensions</span>(<span class="ident">width</span>, <span class="ident">height</span>) {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">ImageError</span>::<span class="ident">FormatError</span>(
<span class="string">"Entry and PNG dimensions do not match!"</span>.<span class="ident">to_string</span>(),
));
}
<span class="comment">// Embedded PNG images can only be of the 32BPP RGBA format.</span>
<span class="comment">// https://blogs.msdn.microsoft.com/oldnewthing/20101022-00/?p=12473/</span>
<span class="kw">let</span> <span class="ident">color_type</span> <span class="op">=</span> <span class="ident">decoder</span>.<span class="ident">colortype</span>();
<span class="kw">if</span> <span class="kw">let</span> <span class="ident">ColorType</span>::<span class="ident">RGBA</span>(<span class="number">8</span>) <span class="op">=</span> <span class="ident">color_type</span> {
} <span class="kw">else</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">ImageError</span>::<span class="ident">FormatError</span>(
<span class="string">"The PNG is not in RGBA format!"</span>.<span class="ident">to_string</span>(),
));
}
<span class="ident">decoder</span>.<span class="ident">read_image</span>()
}
<span class="ident">BMP</span>(<span class="kw-2">mut</span> <span class="ident">decoder</span>) <span class="op">=</span><span class="op">></span> {
<span class="kw">let</span> (<span class="ident">width</span>, <span class="ident">height</span>) <span class="op">=</span> <span class="ident">decoder</span>.<span class="ident">dimensions</span>();
<span class="kw">if</span> <span class="op">!</span><span class="self">self</span>.<span class="ident">selected_entry</span>.<span class="ident">matches_dimensions</span>(<span class="ident">width</span>, <span class="ident">height</span>) {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">ImageError</span>::<span class="ident">FormatError</span>(
<span class="string">"Entry({:?}) and BMP({:?}) dimensions do not match!"</span>.<span class="ident">to_string</span>(),
));
}
<span class="comment">// The ICO decoder needs an alpha channel to apply the AND mask.</span>
<span class="kw">if</span> <span class="ident">decoder</span>.<span class="ident">colortype</span>() <span class="op">!</span><span class="op">=</span> <span class="ident">ColorType</span>::<span class="ident">RGBA</span>(<span class="number">8</span>) {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">ImageError</span>::<span class="ident">UnsupportedError</span>(
<span class="string">"Unsupported color type"</span>.<span class="ident">to_string</span>(),
));
}
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">pixel_data</span> <span class="op">=</span> <span class="ident">decoder</span>.<span class="ident">read_image_data</span>()<span class="question-mark">?</span>;
<span class="comment">// If there's an AND mask following the image, read and apply it.</span>
<span class="kw">let</span> <span class="ident">r</span> <span class="op">=</span> <span class="ident">decoder</span>.<span class="ident">reader</span>();
<span class="kw">let</span> <span class="ident">mask_start</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">seek</span>(<span class="ident">SeekFrom</span>::<span class="ident">Current</span>(<span class="number">0</span>)));
<span class="kw">let</span> <span class="ident">mask_end</span> <span class="op">=</span>
<span class="ident">u64</span>::<span class="ident">from</span>(<span class="self">self</span>.<span class="ident">selected_entry</span>.<span class="ident">image_offset</span> <span class="op">+</span> <span class="self">self</span>.<span class="ident">selected_entry</span>.<span class="ident">image_length</span>);
<span class="kw">let</span> <span class="ident">mask_length</span> <span class="op">=</span> <span class="ident">mask_end</span> <span class="op">-</span> <span class="ident">mask_start</span>;
<span class="kw">if</span> <span class="ident">mask_length</span> <span class="op">></span> <span class="number">0</span> {
<span class="comment">// A mask row contains 1 bit per pixel, padded to 4 bytes.</span>
<span class="kw">let</span> <span class="ident">mask_row_bytes</span> <span class="op">=</span> ((<span class="ident">width</span> <span class="op">+</span> <span class="number">31</span>) <span class="op">/</span> <span class="number">32</span>) <span class="op">*</span> <span class="number">4</span>;
<span class="kw">let</span> <span class="ident">expected_length</span> <span class="op">=</span> <span class="ident">u64</span>::<span class="ident">from</span>(<span class="ident">mask_row_bytes</span> <span class="op">*</span> <span class="ident">height</span>);
<span class="kw">if</span> <span class="ident">mask_length</span> <span class="op"><</span> <span class="ident">expected_length</span> {
<span class="kw">return</span> <span class="prelude-val">Err</span>(<span class="ident">ImageError</span>::<span class="ident">ImageEnd</span>);
}
<span class="kw">for</span> <span class="ident">y</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">height</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">x</span> <span class="op">=</span> <span class="number">0</span>;
<span class="kw">for</span> <span class="kw">_</span> <span class="kw">in</span> <span class="number">0</span>..<span class="ident">mask_row_bytes</span> {
<span class="comment">// Apply the bits of each byte until we reach the end of the row.</span>
<span class="kw">let</span> <span class="ident">mask_byte</span> <span class="op">=</span> <span class="macro">try</span><span class="macro">!</span>(<span class="ident">r</span>.<span class="ident">read_u8</span>());
<span class="kw">for</span> <span class="ident">bit</span> <span class="kw">in</span> (<span class="number">0</span>..<span class="number">8</span>).<span class="ident">rev</span>() {
<span class="kw">if</span> <span class="ident">x</span> <span class="op">></span><span class="op">=</span> <span class="ident">width</span> {
<span class="kw">break</span>;
}
<span class="kw">if</span> <span class="ident">mask_byte</span> <span class="op">&</span> (<span class="number">1</span> <span class="op"><</span><span class="op"><</span> <span class="ident">bit</span>) <span class="op">!</span><span class="op">=</span> <span class="number">0</span> {
<span class="comment">// Set alpha channel to transparent.</span>
<span class="ident">pixel_data</span>[((<span class="ident">height</span> <span class="op">-</span> <span class="ident">y</span> <span class="op">-</span> <span class="number">1</span>) <span class="op">*</span> <span class="ident">width</span> <span class="op">+</span> <span class="ident">x</span>) <span class="kw">as</span> <span class="ident">usize</span> <span class="op">*</span> <span class="number">4</span> <span class="op">+</span> <span class="number">3</span>] <span class="op">=</span> <span class="number">0</span>;
}
<span class="ident">x</span> <span class="op">+</span><span class="op">=</span> <span class="number">1</span>;
}
}
}
}
<span class="prelude-val">Ok</span>(<span class="ident">pixel_data</span>)
}
}
}
}
</pre></div>
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