ios - 从上下文创建子图像
<p><p>我想知道是否有办法创建一个 <code>CGImage</code> 对应于上下文中的一个矩形？</p>
<p>我现在在做什么:</p>
<p>我正在使用 <code>CGBitmapContextCreateImage</code> 从上下文创建 <code>CGImage</code>。然后，我使用 <code>CGImageCreateWithImageInRect</code> 来提取该子图像。</p>
<p>阿尼尔</p></p>
<br><hr><h1><strong>Best Answer-推荐答案</ strong></h1><br>
<p><p>试试这个:</p>
<pre><code>static CGImageRef createImageWithSectionOfBitmapContext(CGContextRef bigContext,
size_t x, size_t y, size_t width, size_t height)
{
uint8_t *data = CGBitmapContextGetData(bigContext);
size_t bytesPerRow = CGBitmapContextGetBytesPerRow(bigContext);
size_t bytesPerPixel = CGBitmapContextGetBitsPerPixel(bigContext) / 8;
data += x * bytesPerPixel + y * bytesPerRow;
CGContextRef smallContext = CGBitmapContextCreate(data,
width, height,
CGBitmapContextGetBitsPerComponent(bigContext), bytesPerRow,
CGBitmapContextGetColorSpace(bigContext),
CGBitmapContextGetBitmapInfo(bigContext));
CGImageRef image = CGBitmapContextCreateImage(smallContext);
CGContextRelease(smallContext);
return image;
}
</code></pre>
<p>或者这个:</p>
<pre><code>static CGImageRef createImageWithSectionOfBitmapContext(CGContextRef bigContext,
size_t x, size_t y, size_t width, size_t height)
{
uint8_t *data = CGBitmapContextGetData(bigContext);
size_t bytesPerRow = CGBitmapContextGetBytesPerRow(bigContext);
size_t bytesPerPixel = CGBitmapContextGetBitsPerPixel(bigContext) / 8;
data += x * bytesPerPixel + y * bytesPerRow;
CGDataProviderRef provider = CGDataProviderCreateWithData(NULL, data,
height * bytesPerRow, NULL);
CGImageRef image = CGImageCreate(width, height,
CGBitmapContextGetBitsPerComponent(bigContext),
CGBitmapContextGetBitsPerPixel(bigContext),
CGBitmapContextGetBytesPerRow(bigContext),
CGBitmapContextGetColorSpace(bigContext),
CGBitmapContextGetBitmapInfo(bigContext),
provider, NULL, NO, kCGRenderingIntentDefault);
CGDataProviderRelease(provider);
return image;
}
</code></pre></p>
<p style="font-size: 20px;">关于ios - 从上下文创建子图像，我们在Stack Overflow上找到一个类似的问题：
<a href="https://stackoverflow.com/questions/13664259/" rel="noreferrer noopener nofollow" style="color: red;">
https://stackoverflow.com/questions/13664259/
</a>
</p>
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