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    FT_Span
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    FT_SpanFunc
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    FT_Raster_Params
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    FT_RASTER_FLAG_XXX
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    FT_Raster
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    FT_Raster_NewFunc
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    FT_Raster_DoneFunc
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    FT_Raster_ResetFunc
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                <p><a href="https://www.freetype.org">FreeType</a> &raquo; <a href="../">Docs</a> &raquo; <a href="index.html#support-api">Support API</a> &raquo; Scanline Converter</p>
<hr />
<h1 id="scanline-converter">Scanline Converter<a class="headerlink" href="#scanline-converter" title="Permanent link">&para;</a></h1>
<h2 id="synopsis">Synopsis<a class="headerlink" href="#synopsis" title="Permanent link">&para;</a></h2>
<p>A raster or a rasterizer is a scan converter in charge of producing a pixel coverage bitmap that can be used as an alpha channel when compositing a glyph with a background. FreeType comes with two rasterizers: bilevel <code>raster1</code> and anti-aliased <code>smooth</code> are two separate modules. They are usually called from the high-level <code><a href="ft2-glyph_retrieval.html#ft_load_glyph">FT_Load_Glyph</a></code> or <code><a href="ft2-glyph_retrieval.html#ft_render_glyph">FT_Render_Glyph</a></code> functions and produce the entire coverage bitmap at once, while staying largely invisible to users.</p>
<p>Instead of working with complete coverage bitmaps, it is also possible to intercept consecutive pixel runs on the same scanline with the same coverage, called <em>spans</em>, and process them individually. Only the <code>smooth</code> rasterizer permits this when calling <code><a href="ft2-outline_processing.html#ft_outline_render">FT_Outline_Render</a></code> with <code><a href="ft2-raster.html#ft_raster_params">FT_Raster_Params</a></code> as described below.</p>
<p>Working with either complete bitmaps or spans it is important to think of them as colorless coverage objects suitable as alpha channels to blend arbitrary colors with a background. For best results, it is recommended to use gamma correction, too.</p>
<p>This section also describes the public API needed to set up alternative <code><a href="ft2-module_management.html#ft_renderer">FT_Renderer</a></code> modules.</p>
<h2 id="ft_span">FT_Span<a class="headerlink" href="#ft_span" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">struct</span>  FT_Span_
  {
    <span class="keyword">short</span>           x;
    <span class="keyword">unsigned</span> <span class="keyword">short</span>  len;
    <span class="keyword">unsigned</span> <span class="keyword">char</span>   coverage;

  } <b>FT_Span</b>;
</code></pre></div>

<p>A structure to model a single span of consecutive pixels when rendering an anti-aliased bitmap.</p>
<h4>fields</h4>
<table class="fields">
<tr><td class="val" id="x">x</td><td class="desc">
<p>The span's horizontal start position.</p>
</td></tr>
<tr><td class="val" id="len">len</td><td class="desc">
<p>The span's length in pixels.</p>
</td></tr>
<tr><td class="val" id="coverage">coverage</td><td class="desc">
<p>The span color/coverage, ranging from 0 (background) to 255 (foreground).</p>
</td></tr>
</table>

<h4>note</h4>

<p>This structure is used by the span drawing callback type named <code><a href="ft2-raster.html#ft_spanfunc">FT_SpanFunc</a></code> that takes the y&nbsp;coordinate of the span as a parameter.</p>
<p>The anti-aliased rasterizer produces coverage values from 0 to 255, that is, from completely transparent to completely opaque.</p>
<hr>

<h2 id="ft_spanfunc">FT_SpanFunc<a class="headerlink" href="#ft_spanfunc" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">void</span>
  (*<b>FT_SpanFunc</b>)( <span class="keyword">int</span>             y,
                  <span class="keyword">int</span>             count,
                  <span class="keyword">const</span> <a href="ft2-raster.html#ft_span">FT_Span</a>*  spans,
                  <span class="keyword">void</span>*           user );

#<span class="keyword">define</span> FT_Raster_Span_Func  <b>FT_SpanFunc</b>
</code></pre></div>

<p>A function used as a call-back by the anti-aliased renderer in order to let client applications draw themselves the pixel spans on each scan line.</p>
<h4>input</h4>
<table class="fields">
<tr><td class="val" id="y">y</td><td class="desc">
<p>The scanline's upward y&nbsp;coordinate.</p>
</td></tr>
<tr><td class="val" id="count">count</td><td class="desc">
<p>The number of spans to draw on this scanline.</p>
</td></tr>
<tr><td class="val" id="spans">spans</td><td class="desc">
<p>A table of <code>count</code> spans to draw on the scanline.</p>
</td></tr>
<tr><td class="val" id="user">user</td><td class="desc">
<p>User-supplied data that is passed to the callback.</p>
</td></tr>
</table>

<h4>note</h4>

<p>This callback allows client applications to directly render the spans of the anti-aliased bitmap to any kind of surfaces.</p>
<p>This can be used to write anti-aliased outlines directly to a given background bitmap using alpha compositing. It can also be used for oversampling and averaging.</p>
<hr>

<h2 id="ft_raster_params">FT_Raster_Params<a class="headerlink" href="#ft_raster_params" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">struct</span>  FT_Raster_Params_
  {
    <span class="keyword">const</span> <a href="ft2-basic_types.html#ft_bitmap">FT_Bitmap</a>*        target;
    <span class="keyword">const</span> <span class="keyword">void</span>*             source;
    <span class="keyword">int</span>                     flags;
    <a href="ft2-raster.html#ft_spanfunc">FT_SpanFunc</a>             gray_spans;
    <a href="ft2-raster.html#ft_spanfunc">FT_SpanFunc</a>             black_spans;  /* unused */
    <a href="ft2-raster.html#ft_raster_bittest_func">FT_Raster_BitTest_Func</a>  bit_test;     /* unused */
    <a href="ft2-raster.html#ft_raster_bitset_func">FT_Raster_BitSet_Func</a>   bit_set;      /* unused */
    <span class="keyword">void</span>*                   user;
    <a href="ft2-basic_types.html#ft_bbox">FT_BBox</a>                 clip_box;

  } <b>FT_Raster_Params</b>;
</code></pre></div>

<p>A structure to hold the parameters used by a raster's render function, passed as an argument to <code><a href="ft2-outline_processing.html#ft_outline_render">FT_Outline_Render</a></code>.</p>
<h4>fields</h4>
<table class="fields">
<tr><td class="val" id="target">target</td><td class="desc">
<p>The target bitmap.</p>
</td></tr>
<tr><td class="val" id="source">source</td><td class="desc">
<p>A pointer to the source glyph image (e.g., an <code><a href="ft2-outline_processing.html#ft_outline">FT_Outline</a></code>).</p>
</td></tr>
<tr><td class="val" id="flags">flags</td><td class="desc">
<p>The rendering flags.</p>
</td></tr>
<tr><td class="val" id="gray_spans">gray_spans</td><td class="desc">
<p>The gray span drawing callback.</p>
</td></tr>
<tr><td class="val" id="black_spans">black_spans</td><td class="desc">
<p>Unused.</p>
</td></tr>
<tr><td class="val" id="bit_test">bit_test</td><td class="desc">
<p>Unused.</p>
</td></tr>
<tr><td class="val" id="bit_set">bit_set</td><td class="desc">
<p>Unused.</p>
</td></tr>
<tr><td class="val" id="user">user</td><td class="desc">
<p>User-supplied data that is passed to each drawing callback.</p>
</td></tr>
<tr><td class="val" id="clip_box">clip_box</td><td class="desc">
<p>An optional span clipping box expressed in <em>integer</em> pixels (not in 26.6 fixed-point units).</p>
</td></tr>
</table>

<h4>note</h4>

<p>The <code><a href="ft2-raster.html#ft_raster_flag_xxx">FT_RASTER_FLAG_AA</a></code> bit flag must be set in the <code>flags</code> to generate an anti-aliased glyph bitmap, otherwise a monochrome bitmap is generated. The <code>target</code> should have appropriate pixel mode and its dimensions define the clipping region.</p>
<p>If both <code><a href="ft2-raster.html#ft_raster_flag_xxx">FT_RASTER_FLAG_AA</a></code> and <code><a href="ft2-raster.html#ft_raster_flag_xxx">FT_RASTER_FLAG_DIRECT</a></code> bit flags are set in <code>flags</code>, the raster calls an <code><a href="ft2-raster.html#ft_spanfunc">FT_SpanFunc</a></code> callback <code>gray_spans</code> with <code>user</code> data as an argument ignoring <code>target</code>. This allows direct composition over a pre-existing user surface to perform the span drawing and composition. To optionally clip the spans, set the <code><a href="ft2-raster.html#ft_raster_flag_xxx">FT_RASTER_FLAG_CLIP</a></code> flag and <code>clip_box</code>. The monochrome raster does not support the direct mode.</p>
<p>The gray-level rasterizer always uses 256 gray levels. If you want fewer gray levels, you have to use <code><a href="ft2-raster.html#ft_raster_flag_xxx">FT_RASTER_FLAG_DIRECT</a></code> and reduce the levels in the callback function.</p>
<hr>

<h2 id="ft_raster_flag_xxx">FT_RASTER_FLAG_XXX<a class="headerlink" href="#ft_raster_flag_xxx" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>#<span class="keyword">define</span> <a href="ft2-raster.html#ft_raster_flag_default">FT_RASTER_FLAG_DEFAULT</a>  0x0
#<span class="keyword">define</span> <a href="ft2-raster.html#ft_raster_flag_aa">FT_RASTER_FLAG_AA</a>       0x1
#<span class="keyword">define</span> <a href="ft2-raster.html#ft_raster_flag_direct">FT_RASTER_FLAG_DIRECT</a>   0x2
#<span class="keyword">define</span> <a href="ft2-raster.html#ft_raster_flag_clip">FT_RASTER_FLAG_CLIP</a>     0x4
#<span class="keyword">define</span> <a href="ft2-raster.html#ft_raster_flag_sdf">FT_RASTER_FLAG_SDF</a>      0x8

  /* these constants are deprecated; use the corresponding */
  /* `<b>FT_RASTER_FLAG_XXX</b>` values instead                   */
#<span class="keyword">define</span> ft_raster_flag_default  <a href="ft2-raster.html#ft_raster_flag_default">FT_RASTER_FLAG_DEFAULT</a>
#<span class="keyword">define</span> ft_raster_flag_aa       <a href="ft2-raster.html#ft_raster_flag_aa">FT_RASTER_FLAG_AA</a>
#<span class="keyword">define</span> ft_raster_flag_direct   <a href="ft2-raster.html#ft_raster_flag_direct">FT_RASTER_FLAG_DIRECT</a>
#<span class="keyword">define</span> ft_raster_flag_clip     <a href="ft2-raster.html#ft_raster_flag_clip">FT_RASTER_FLAG_CLIP</a>
</code></pre></div>

<p>A list of bit flag constants as used in the <code>flags</code> field of a <code><a href="ft2-raster.html#ft_raster_params">FT_Raster_Params</a></code> structure.</p>
<h4>values</h4>
<table class="fields">
<tr><td class="val" id="ft_raster_flag_default">FT_RASTER_FLAG_DEFAULT</td><td class="desc">
<p>This value is 0.</p>
</td></tr>
<tr><td class="val" id="ft_raster_flag_aa">FT_RASTER_FLAG_AA</td><td class="desc">
<p>This flag is set to indicate that an anti-aliased glyph image should be generated. Otherwise, it will be monochrome (1-bit).</p>
</td></tr>
<tr><td class="val" id="ft_raster_flag_direct">FT_RASTER_FLAG_DIRECT</td><td class="desc">
<p>This flag is set to indicate direct rendering. In this mode, client applications must provide their own span callback. This lets them directly draw or compose over an existing bitmap. If this bit is <em>not</em> set, the target pixmap's buffer <em>must</em> be zeroed before rendering and the output will be clipped to its size.</p>
<p>Direct rendering is only possible with anti-aliased glyphs.</p>
</td></tr>
<tr><td class="val" id="ft_raster_flag_clip">FT_RASTER_FLAG_CLIP</td><td class="desc">
<p>This flag is only used in direct rendering mode. If set, the output will be clipped to a box specified in the <code>clip_box</code> field of the <code><a href="ft2-raster.html#ft_raster_params">FT_Raster_Params</a></code> structure. Otherwise, the <code>clip_box</code> is effectively set to the bounding box and all spans are generated.</p>
</td></tr>
<tr><td class="val" id="ft_raster_flag_sdf">FT_RASTER_FLAG_SDF</td><td class="desc">
<p>This flag is set to indicate that a signed distance field glyph image should be generated. This is only used while rendering with the <code><a href="ft2-glyph_retrieval.html#ft_render_mode">FT_RENDER_MODE_SDF</a></code> render mode.</p>
</td></tr>
</table>

<hr>

<h2 id="ft_raster">FT_Raster<a class="headerlink" href="#ft_raster" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">struct</span> FT_RasterRec_*  <b>FT_Raster</b>;
</code></pre></div>

<p>An opaque handle (pointer) to a raster object. Each object can be used independently to convert an outline into a bitmap or pixmap.</p>
<h4>note</h4>

<p>In FreeType 2, all rasters are now encapsulated within specific <code><a href="ft2-module_management.html#ft_renderer">FT_Renderer</a></code> modules and only used in their context.</p>
<hr>

<h2 id="ft_raster_newfunc">FT_Raster_NewFunc<a class="headerlink" href="#ft_raster_newfunc" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">int</span>
  (*<b>FT_Raster_NewFunc</b>)( <span class="keyword">void</span>*       memory,
                        <a href="ft2-raster.html#ft_raster">FT_Raster</a>*  raster );

#<span class="keyword">define</span> FT_Raster_New_Func  <b>FT_Raster_NewFunc</b>
</code></pre></div>

<p>A function used to create a new raster object.</p>
<h4>input</h4>
<table class="fields">
<tr><td class="val" id="memory">memory</td><td class="desc">
<p>A handle to the memory allocator.</p>
</td></tr>
</table>

<h4>output</h4>
<table class="fields">
<tr><td class="val" id="raster">raster</td><td class="desc">
<p>A handle to the new raster object.</p>
</td></tr>
</table>

<h4>return</h4>

<p>Error code. 0&nbsp;means success.</p>
<h4>note</h4>

<p>The <code>memory</code> parameter is a typeless pointer in order to avoid un-wanted dependencies on the rest of the FreeType code. In practice, it is an <code><a href="ft2-system_interface.html#ft_memory">FT_Memory</a></code> object, i.e., a handle to the standard FreeType memory allocator. However, this field can be completely ignored by a given raster implementation.</p>
<hr>

<h2 id="ft_raster_donefunc">FT_Raster_DoneFunc<a class="headerlink" href="#ft_raster_donefunc" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">void</span>
  (*<b>FT_Raster_DoneFunc</b>)( <a href="ft2-raster.html#ft_raster">FT_Raster</a>  raster );

#<span class="keyword">define</span> FT_Raster_Done_Func  <b>FT_Raster_DoneFunc</b>
</code></pre></div>

<p>A function used to destroy a given raster object.</p>
<h4>input</h4>
<table class="fields">
<tr><td class="val" id="raster">raster</td><td class="desc">
<p>A handle to the raster object.</p>
</td></tr>
</table>

<hr>

<h2 id="ft_raster_resetfunc">FT_Raster_ResetFunc<a class="headerlink" href="#ft_raster_resetfunc" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">void</span>
  (*<b>FT_Raster_ResetFunc</b>)( <a href="ft2-raster.html#ft_raster">FT_Raster</a>       raster,
                          <span class="keyword">unsigned</span> <span class="keyword">char</span>*  pool_base,
                          <span class="keyword">unsigned</span> <span class="keyword">long</span>   pool_size );

#<span class="keyword">define</span> FT_Raster_Reset_Func  <b>FT_Raster_ResetFunc</b>
</code></pre></div>

<p>FreeType used to provide an area of memory called the &lsquo;render pool&rsquo; available to all registered rasterizers. This was not thread safe, however, and now FreeType never allocates this pool.</p>
<p>This function is called after a new raster object is created.</p>
<h4>input</h4>
<table class="fields">
<tr><td class="val" id="raster">raster</td><td class="desc">
<p>A handle to the new raster object.</p>
</td></tr>
<tr><td class="val" id="pool_base">pool_base</td><td class="desc">
<p>Previously, the address in memory of the render pool. Set this to <code>NULL</code>.</p>
</td></tr>
<tr><td class="val" id="pool_size">pool_size</td><td class="desc">
<p>Previously, the size in bytes of the render pool. Set this to 0.</p>
</td></tr>
</table>

<h4>note</h4>

<p>Rasterizers should rely on dynamic or stack allocation if they want to (a handle to the memory allocator is passed to the rasterizer constructor).</p>
<hr>

<h2 id="ft_raster_setmodefunc">FT_Raster_SetModeFunc<a class="headerlink" href="#ft_raster_setmodefunc" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">int</span>
  (*<b>FT_Raster_SetModeFunc</b>)( <a href="ft2-raster.html#ft_raster">FT_Raster</a>      raster,
                            <span class="keyword">unsigned</span> <span class="keyword">long</span>  mode,
                            <span class="keyword">void</span>*          args );

#<span class="keyword">define</span> FT_Raster_Set_Mode_Func  <b>FT_Raster_SetModeFunc</b>
</code></pre></div>

<p>This function is a generic facility to change modes or attributes in a given raster. This can be used for debugging purposes, or simply to allow implementation-specific &lsquo;features&rsquo; in a given raster module.</p>
<h4>input</h4>
<table class="fields">
<tr><td class="val" id="raster">raster</td><td class="desc">
<p>A handle to the new raster object.</p>
</td></tr>
<tr><td class="val" id="mode">mode</td><td class="desc">
<p>A 4-byte tag used to name the mode or property.</p>
</td></tr>
<tr><td class="val" id="args">args</td><td class="desc">
<p>A pointer to the new mode/property to use.</p>
</td></tr>
</table>

<hr>

<h2 id="ft_raster_renderfunc">FT_Raster_RenderFunc<a class="headerlink" href="#ft_raster_renderfunc" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">int</span>
  (*<b>FT_Raster_RenderFunc</b>)( <a href="ft2-raster.html#ft_raster">FT_Raster</a>                raster,
                           <span class="keyword">const</span> <a href="ft2-raster.html#ft_raster_params">FT_Raster_Params</a>*  params );

#<span class="keyword">define</span> FT_Raster_Render_Func  <b>FT_Raster_RenderFunc</b>
</code></pre></div>

<p>Invoke a given raster to scan-convert a given glyph image into a target bitmap.</p>
<h4>input</h4>
<table class="fields">
<tr><td class="val" id="raster">raster</td><td class="desc">
<p>A handle to the raster object.</p>
</td></tr>
<tr><td class="val" id="params">params</td><td class="desc">
<p>A pointer to an <code><a href="ft2-raster.html#ft_raster_params">FT_Raster_Params</a></code> structure used to store the rendering parameters.</p>
</td></tr>
</table>

<h4>return</h4>

<p>Error code. 0&nbsp;means success.</p>
<h4>note</h4>

<p>The exact format of the source image depends on the raster's glyph format defined in its <code><a href="ft2-raster.html#ft_raster_funcs">FT_Raster_Funcs</a></code> structure. It can be an <code><a href="ft2-outline_processing.html#ft_outline">FT_Outline</a></code> or anything else in order to support a large array of glyph formats.</p>
<p>Note also that the render function can fail and return a <code>FT_Err_Unimplemented_Feature</code> error code if the raster used does not support direct composition.</p>
<hr>

<h2 id="ft_raster_funcs">FT_Raster_Funcs<a class="headerlink" href="#ft_raster_funcs" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">struct</span>  FT_Raster_Funcs_
  {
    <a href="ft2-basic_types.html#ft_glyph_format">FT_Glyph_Format</a>        glyph_format;

    <a href="ft2-raster.html#ft_raster_newfunc">FT_Raster_NewFunc</a>      raster_new;
    <a href="ft2-raster.html#ft_raster_resetfunc">FT_Raster_ResetFunc</a>    raster_reset;
    <a href="ft2-raster.html#ft_raster_setmodefunc">FT_Raster_SetModeFunc</a>  raster_set_mode;
    <a href="ft2-raster.html#ft_raster_renderfunc">FT_Raster_RenderFunc</a>   raster_render;
    <a href="ft2-raster.html#ft_raster_donefunc">FT_Raster_DoneFunc</a>     raster_done;

  } <b>FT_Raster_Funcs</b>;
</code></pre></div>

<p>A structure used to describe a given raster class to the library.</p>
<h4>fields</h4>
<table class="fields">
<tr><td class="val" id="glyph_format">glyph_format</td><td class="desc">
<p>The supported glyph format for this raster.</p>
</td></tr>
<tr><td class="val" id="raster_new">raster_new</td><td class="desc">
<p>The raster constructor.</p>
</td></tr>
<tr><td class="val" id="raster_reset">raster_reset</td><td class="desc">
<p>Used to reset the render pool within the raster.</p>
</td></tr>
<tr><td class="val" id="raster_render">raster_render</td><td class="desc">
<p>A function to render a glyph into a given bitmap.</p>
</td></tr>
<tr><td class="val" id="raster_done">raster_done</td><td class="desc">
<p>The raster destructor.</p>
</td></tr>
</table>

<hr>

<h2 id="ft_raster_bittest_func">FT_Raster_BitTest_Func<a class="headerlink" href="#ft_raster_bittest_func" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">int</span>
  (*<b>FT_Raster_BitTest_Func</b>)( <span class="keyword">int</span>    y,
                             <span class="keyword">int</span>    x,
                             <span class="keyword">void</span>*  user );
</code></pre></div>

<p>Deprecated, unimplemented.</p>
<hr>

<h2 id="ft_raster_bitset_func">FT_Raster_BitSet_Func<a class="headerlink" href="#ft_raster_bitset_func" title="Permanent link">&para;</a></h2>
<p>Defined in FT_IMAGE_H (freetype/ftimage.h).</p>
<div class = "codehilite"><pre><code>  <span class="keyword">typedef</span> <span class="keyword">void</span>
  (*<b>FT_Raster_BitSet_Func</b>)( <span class="keyword">int</span>    y,
                            <span class="keyword">int</span>    x,
                            <span class="keyword">void</span>*  user );
</code></pre></div>

<p>Deprecated, unimplemented.</p>
<hr>
                
              
              
                


              
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