# ImageMagick – MagickCore, C API: Add a Special Effect
ImageMagick is a powerful, open-source software suite for creating, editing, converting, and manipulating images in over 200 formats. Ideal for web developers, graphic designers, and researchers, it offers versatile tools for image processing, including batch processing, format conversion, and complex image transformations.
Keywords: MagickCore, C API: Add a Special Effect, Image Processing, Digital Image Editing, Image Conversion, Open-Source Software, Image Manipulation, Command-Line Image Tools

# Fx

## pfx->exception, GetMagickModule

pfx->exception, GetMagickModule(), OptionError, "ImgNum", "lu bad for ImgListLen lu", (unsigned long) i, (unsigned long) pfx->ImgListLen); i = -1; } return i; }

#define WHICH_ATTR_CHAN \ (pel->channel_qual == NO_CHAN_QUAL) ? CompositePixelChannel : \ (pel->channel_qual == THIS_CHANNEL) ? channel : pel->channel_qual

#define WHICH_NON_ATTR_CHAN \ (pel->channel_qual == NO_CHAN_QUAL || \ pel->channel_qual == THIS_CHANNEL || \ pel->channel_qual == CompositePixelChannel \ ) ? (channel == CompositePixelChannel ? RedPixelChannel: channel) \ : pel->channel_qual

static fxFltType GetHslFlt (FxInfo * pfx, ssize_t ImgNum, const fxFltType fx, const fxFltType fy, PixelChannel channel) { Image * img = pfx->Images[ImgNum];

double red, green, blue; double hue=0, saturation=0, lightness=0;

MagickBooleanType okay = MagickTrue; if(!InterpolatePixelChannel (img, pfx->Imgs[ImgNum].View, RedPixelChannel, img->interpolate, (double) fx, (double) fy, &red, pfx->exception)) okay = MagickFalse; if(!InterpolatePixelChannel (img, pfx->Imgs[ImgNum].View, GreenPixelChannel, img->interpolate, (double) fx, (double) fy, &green, pfx->exception)) okay = MagickFalse; if(!InterpolatePixelChannel (img, pfx->Imgs[ImgNum].View, BluePixelChannel, img->interpolate, (double) fx, (double) fy, &blue, pfx->exception)) okay = MagickFalse;

if (!okay) (void) ThrowMagickException ( pfx->exception, GetMagickModule(), OptionError, "GetHslFlt failure", "lu g,g i", (unsigned long) ImgNum, (double) fx, (double) fy, channel);

ConvertRGBToHSL ( red, green, blue, &hue, &saturation, &lightness);

if (channel == HUE_CHANNEL) return hue; if (channel == SAT_CHANNEL) return saturation; if (channel == LIGHT_CHANNEL) return lightness;

return 0.0; }

static fxFltType GetHslInt (FxInfo * pfx, ssize_t ImgNum, const ssize_t imgx, const ssize_t imgy, PixelChannel channel) { Image * img = pfx->Images[ImgNum];

double hue=0, saturation=0, lightness=0;

const Quantum * p = GetCacheViewVirtualPixels (pfx->Imgs[ImgNum].View, imgx, imgy, 1, 1, pfx->exception); if (p == (const Quantum *) NULL) { (void) ThrowMagickException (pfx->exception,GetMagickModule(), OptionError,"GetHslInt failure","lu li,li i",(unsigned long) ImgNum, (long) imgx,(long) imgy,channel); return(0.0); }

ConvertRGBToHSL ( GetPixelRed (img, p), GetPixelGreen (img, p), GetPixelBlue (img, p), &hue, &saturation, &lightness);

if (channel == HUE_CHANNEL) return hue; if (channel == SAT_CHANNEL) return saturation; if (channel == LIGHT_CHANNEL) return lightness;

return 0.0; }

static inline fxFltType GetIntensity (FxInfo * pfx, ssize_t ImgNum, const fxFltType fx, const fxFltType fy) { Quantum quantum_pixel[MaxPixelChannels];

PixelInfo pixelinf;

Image * img = pfx->Images[ImgNum];

(void) GetPixelInfo (img, &pixelinf);

if (!InterpolatePixelInfo (img, pfx->Imgs[pfx->ImgNum].View, img->interpolate, (double) fx, (double) fy, &pixelinf, pfx->exception)) { (void) ThrowMagickException ( pfx->exception, GetMagickModule(), OptionError, "GetIntensity failure", "lu g,g", (unsigned long) ImgNum, (double) fx, (double) fy); }

SetPixelViaPixelInfo (img, &pixelinf, quantum_pixel); return QuantumScale * GetPixelIntensity (img, quantum_pixel); }

static MagickBooleanType ExecuteRPN (FxInfo * pfx, fxRtT * pfxrt, fxFltType *result, const PixelChannel channel, const ssize_t imgx, const ssize_t imgy) { const Quantum * p = pfxrt->thisPixel; fxFltType regA=0, regB=0, regC=0, regD=0, regE=0; Image * img = pfx->image; ChannelStatistics * cs = NULL; MagickBooleanType NeedRelinq = MagickFalse; double hue=0, saturation=0, lightness=0; int i;

/* For -fx, this sets p to ImgNum 0. for [fx:...], this sets p to the current image. Similarly img.