GraphicsMagick 的 OpenCL 开发记录（十）

<2022-03-18 Fri>

关于gpuSupportedResizeWeighting()的代码能否省略

在ImageMagick的AccelerateResizeImage()函数中有这样的一段代码被注释掉了：

// if ((gpuSupportedResizeWeighting(GetResizeFilterWeightingType(
//        resizeFilter)) == MagickFalse) ||
//     (gpuSupportedResizeWeighting(GetResizeFilterWindowWeightingType(
//        resizeFilter)) == MagickFalse))
//   return((Image *) NULL);

我认为这段代码可以省略，因为它的目的就是为了检查ImageMagick的ResizeFilter类型中的ResizeWeightingFunctionType类型的成员值：

struct _ResizeFilter
{
  double
    (*filter)(const double,const ResizeFilter *),
    (*window)(const double,const ResizeFilter *),
    support,        /* filter region of support - the filter support limit */
    window_support, /* window support, usally equal to support (expert only) */
    scale,          /* dimension scaling to fit window support (usally 1.0) */
    blur,           /* x-scale (blur-sharpen) */
    coefficient[7]; /* cubic coefficents for BC-cubic filters */

  ResizeWeightingFunctionType
    filterWeightingType,
    windowWeightingType;

  size_t
    signature;
};

是否在supportedResizeWeighting数组中：

static const ResizeWeightingFunctionType supportedResizeWeighting[] =
{
  BoxWeightingFunction,
  TriangleWeightingFunction,
  HannWeightingFunction,
  HammingWeightingFunction,
  BlackmanWeightingFunction,
  CubicBCWeightingFunction,
  SincWeightingFunction,
  SincFastWeightingFunction,
  LastWeightingFunction
};

很明显这个数组就是ImageMagick支持GPU的窗函数集合。在GraphicsMagick中我只在ResizeImage()函数中找到相近的定义：

static const FilterInfo
  filters[SincFilter+1] =
  {
    { Box, 0.0 },
    { Box, 0.0 },
    { Box, 0.5 },
    { Triangle, 1.0 },
    { Hermite, 1.0 },
    { Hanning, 1.0 },
    { Hamming, 1.0 },
    { Blackman, 1.0 },
    { Gaussian, 1.25 },
    { Quadratic, 1.5 },
    { Cubic, 2.0 },
    { Catrom, 2.0 },
    { Mitchell, 2.0 },
    { Lanczos, 3.0 },
    { BlackmanBessel, 3.2383 },
    { BlackmanSinc, 4.0 }
  };

明显可见，GraphicsMagick中处理相对于ImageMagick简单多了，所以上面的代码我仍然保持它被注释状态。

原文地址：https://blog.csdn.net/ftuc5dn/article/details/135712324

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