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libgd/src/gd_filter.c

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/**
* File: Image Filters
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "gd.h"
#include "gdhelpers.h"
#include "gd_intern.h"
#ifdef _WIN32
# include <windows.h>
#else
# include <unistd.h>
#endif
#include <stdlib.h>
#include <time.h>
#include <math.h>
#undef NDEBUG
/* Comment out this line to enable asserts.
* TODO: This logic really belongs in cmake and configure.
*/
#define NDEBUG 1
#include <assert.h>
typedef int (BGD_STDCALL *FuncPtr)(gdImagePtr, int, int);
#define GET_PIXEL_FUNCTION(src)(src->trueColor?gdImageGetTrueColorPixel:gdImageGetPixel)
#ifdef _WIN32
# define GD_SCATTER_SEED() (unsigned int)(time(0) * GetCurrentProcessId())
#else
# define GD_SCATTER_SEED() (unsigned int)(time(0) * getpid())
#endif
/*
Function: gdImageScatter
*/
BGD_DECLARE(int) gdImageScatter(gdImagePtr im, int sub, int plus)
{
gdScatter s;
s.sub = sub;
s.plus = plus;
s.num_colors = 0;
s.seed = GD_SCATTER_SEED();
return gdImageScatterEx(im, &s);
}
/*
Function: gdImageScatterColor
*/
BGD_DECLARE(int) gdImageScatterColor(gdImagePtr im, int sub, int plus, int colors[], unsigned int num_colors)
{
gdScatter s;
s.sub = sub;
s.plus = plus;
s.colors = colors;
s.num_colors = num_colors;
s.seed = GD_SCATTER_SEED();
return gdImageScatterEx(im, &s);
}
/*
Function: gdImageScatterEx
*/
BGD_DECLARE(int) gdImageScatterEx(gdImagePtr im, gdScatterPtr scatter)
{
register int x, y;
int dest_x, dest_y;
int pxl, new_pxl;
unsigned int n;
int sub = scatter->sub, plus = scatter->plus;
if (plus == 0 && sub == 0) {
return 1;
} else if (sub >= plus) {
return 0;
}
(void)srand(scatter->seed);
if (scatter->num_colors) {
for (y = 0; y < im->sy; y++) {
for (x = 0; x < im->sx; x++) {
dest_x = (int) (x + ((rand() % (plus - sub)) + sub));
dest_y = (int) (y + ((rand() % (plus - sub)) + sub));
if (!gdImageBoundsSafe(im, dest_x, dest_y)) {
continue;
}
pxl = gdImageGetPixel(im, x, y);
new_pxl = gdImageGetPixel(im, dest_x, dest_y);
for (n = 0; n < scatter->num_colors; n++) {
if (pxl == scatter->colors[n]) {
gdImageSetPixel(im, dest_x, dest_y, pxl);
gdImageSetPixel(im, x, y, new_pxl);
}
}
}
}
} else {
for (y = 0; y < im->sy; y++) {
for (x = 0; x < im->sx; x++) {
dest_x = (int) (x + ((rand() % (plus - sub)) + sub));
dest_y = (int) (y + ((rand() % (plus - sub)) + sub));
if (!gdImageBoundsSafe(im, dest_x, dest_y)) {
continue;
}
pxl = gdImageGetPixel(im, x, y);
new_pxl = gdImageGetPixel(im, dest_x, dest_y);
gdImageSetPixel(im, dest_x, dest_y, pxl);
gdImageSetPixel(im, x, y, new_pxl);
}
}
}
return 1;
}
/*
Function: gdImagePixelate
*/
BGD_DECLARE(int) gdImagePixelate(gdImagePtr im, int block_size, const unsigned int mode)
{
int x, y;
if (block_size <= 0) {
return 0;
} else if (block_size == 1) {
return 1;
}
switch (mode) {
case GD_PIXELATE_UPPERLEFT:
for (y = 0; y < im->sy; y += block_size) {
for (x = 0; x < im->sx; x += block_size) {
if (gdImageBoundsSafe(im, x, y)) {
int c = gdImageGetPixel(im, x, y);
gdImageFilledRectangle(im, x, y, x + block_size - 1, y + block_size - 1, c);
}
}
}
break;
case GD_PIXELATE_AVERAGE:
for (y = 0; y < im->sy; y += block_size) {
for (x = 0; x < im->sx; x += block_size) {
int a, r, g, b, c;
int total;
int cx, cy;
a = r = g = b = c = total = 0;
/* sampling */
for (cy = 0; cy < block_size; cy++) {
for (cx = 0; cx < block_size; cx++) {
if (!gdImageBoundsSafe(im, x + cx, y + cy)) {
continue;
}
c = gdImageGetPixel(im, x + cx, y + cy);
a += gdImageAlpha(im, c);
r += gdImageRed(im, c);
g += gdImageGreen(im, c);
b += gdImageBlue(im, c);
total++;
}
}
/* drawing */
if (total > 0) {
c = gdImageColorResolveAlpha(im, r / total, g / total, b / total, a / total);
gdImageFilledRectangle(im, x, y, x + block_size - 1, y + block_size - 1, c);
}
}
}
break;
default:
return 0;
}
return 1;
}
/**
* Function: gdImageNegate
*
* Invert an image
*
* Parameters:
* src - The image.
*
* Returns:
* Non-zero on success, zero on failure.
*/
BGD_DECLARE(int) gdImageNegate(gdImagePtr src)
{
int x, y;
int r,g,b,a;
int new_pxl, pxl;
FuncPtr f;
if (src==NULL) {
return 0;
}
f = GET_PIXEL_FUNCTION(src);
for (y=0; y<src->sy; ++y) {
for (x=0; x<src->sx; ++x) {
pxl = f (src, x, y);
r = gdImageRed(src, pxl);
g = gdImageGreen(src, pxl);
b = gdImageBlue(src, pxl);
a = gdImageAlpha(src, pxl);
new_pxl = gdImageColorAllocateAlpha(src, 255-r, 255-g, 255-b, a);
if (new_pxl == -1) {
new_pxl = gdImageColorClosestAlpha(src, 255-r, 255-g, 255-b, a);
}
gdImageSetPixel (src, x, y, new_pxl);
}
}
return 1;
}
/**
* Function: gdImageGrayScale
*
* Convert an image to grayscale
*
* The red, green and blue components of each pixel are replaced by their
* weighted sum using the same coefficients as the REC.601 luma (Y')
* calculation. The alpha components are retained.
*
* For palette images the result may differ due to palette limitations.
*
* Parameters:
* src - The image.
*
* Returns:
* Non-zero on success, zero on failure.
*/
BGD_DECLARE(int) gdImageGrayScale(gdImagePtr src)
{
int x, y;
int r,g,b,a;
int new_pxl, pxl;
FuncPtr f;
int alpha_blending;
if (src==NULL) {
return 0;
}
alpha_blending = src->alphaBlendingFlag;
gdImageAlphaBlending(src, gdEffectReplace);
f = GET_PIXEL_FUNCTION(src);
for (y=0; y<src->sy; ++y) {
for (x=0; x<src->sx; ++x) {
pxl = f (src, x, y);
r = gdImageRed(src, pxl);
g = gdImageGreen(src, pxl);
b = gdImageBlue(src, pxl);
a = gdImageAlpha(src, pxl);
r = g = b = (int) (.299 * r + .587 * g + .114 * b);
new_pxl = gdImageColorAllocateAlpha(src, r, g, b, a);
if (new_pxl == -1) {
new_pxl = gdImageColorClosestAlpha(src, r, g, b, a);
}
gdImageSetPixel (src, x, y, new_pxl);
}
}
gdImageAlphaBlending(src, alpha_blending);
return 1;
}
/**
* Function: gdImageBrightness
*
* Change the brightness of an image
*
* Parameters:
* src - The image.
* brightness - The value to add to the color channels of all pixels.
*
* Returns:
* Non-zero on success, zero on failure.
*
* See also:
* - <gdImageContrast>
* - <gdImageColor>
*/
BGD_DECLARE(int) gdImageBrightness(gdImagePtr src, int brightness)
{
int x, y;
int r,g,b,a;
int new_pxl, pxl;
FuncPtr f;
if (src==NULL || (brightness < -255 || brightness > 255)) {
return 0;
}
if (brightness==0) {
return 1;
}
f = GET_PIXEL_FUNCTION(src);
for (y=0; y<src->sy; ++y) {
for (x=0; x<src->sx; ++x) {
pxl = f (src, x, y);
r = gdImageRed(src, pxl);
g = gdImageGreen(src, pxl);
b = gdImageBlue(src, pxl);
a = gdImageAlpha(src, pxl);
r = r + brightness;
g = g + brightness;
b = b + brightness;
r = (r > 255)? 255 : ((r < 0)? 0:r);
g = (g > 255)? 255 : ((g < 0)? 0:g);
b = (b > 255)? 255 : ((b < 0)? 0:b);
new_pxl = gdImageColorAllocateAlpha(src, (int)r, (int)g, (int)b, a);
if (new_pxl == -1) {
new_pxl = gdImageColorClosestAlpha(src, (int)r, (int)g, (int)b, a);
}
gdImageSetPixel (src, x, y, new_pxl);
}
}
return 1;
}
/**
* Function: gdImageContrast
*
* Change the contrast of an image
*
* Parameters:
* src - The image.
* contrast - The contrast adjustment value. Negative values increase, postive
* values decrease the contrast. The larger the absolute value, the
* stronger the effect.
*
* Returns:
* Non-zero on success, zero on failure.
*
* See also:
* - <gdImageBrightness>
*/
BGD_DECLARE(int) gdImageContrast(gdImagePtr src, double contrast)
{
int x, y;
int r,g,b,a;
double rf,gf,bf;
int new_pxl, pxl;
FuncPtr f;
if (src==NULL) {
return 0;
}
f = GET_PIXEL_FUNCTION(src);
contrast = (double)(100.0-contrast)/100.0;
contrast = contrast*contrast;
for (y=0; y<src->sy; ++y) {
for (x=0; x<src->sx; ++x) {
pxl = f(src, x, y);
r = gdImageRed(src, pxl);
g = gdImageGreen(src, pxl);
b = gdImageBlue(src, pxl);
a = gdImageAlpha(src, pxl);
rf = (double)r/255.0;
rf = rf-0.5;
rf = rf*contrast;
rf = rf+0.5;
rf = rf*255.0;
bf = (double)b/255.0;
bf = bf-0.5;
bf = bf*contrast;
bf = bf+0.5;
bf = bf*255.0;
gf = (double)g/255.0;
gf = gf-0.5;
gf = gf*contrast;
gf = gf+0.5;
gf = gf*255.0;
rf = (rf > 255.0)? 255.0 : ((rf < 0.0)? 0.0:rf);
gf = (gf > 255.0)? 255.0 : ((gf < 0.0)? 0.0:gf);
bf = (bf > 255.0)? 255.0 : ((bf < 0.0)? 0.0:bf);
new_pxl = gdImageColorAllocateAlpha(src, (int)rf, (int)gf, (int)bf, a);
if (new_pxl == -1) {
new_pxl = gdImageColorClosestAlpha(src, (int)rf, (int)gf, (int)bf, a);
}
gdImageSetPixel (src, x, y, new_pxl);
}
}
return 1;
}
/**
* Function: gdImageColor
*
* Change channel values of an image
*
* Parameters:
* src - The image.
* red - The value to add to the red channel of all pixels.
* green - The value to add to the green channel of all pixels.
* blue - The value to add to the blue channel of all pixels.
* alpha - The value to add to the alpha channel of all pixels.
*
* Returns:
* Non-zero on success, zero on failure.
*
* See also:
* - <gdImageBrightness>
*/
BGD_DECLARE(int) gdImageColor(gdImagePtr src, const int red, const int green, const int blue, const int alpha)
{
int x, y;
int new_pxl, pxl;
FuncPtr f;
if (src == NULL) {
return 0;
}
f = GET_PIXEL_FUNCTION(src);
for (y=0; y<src->sy; ++y) {
for (x=0; x<src->sx; ++x) {
int r,g,b,a;
pxl = f(src, x, y);
r = gdImageRed(src, pxl);
g = gdImageGreen(src, pxl);
b = gdImageBlue(src, pxl);
a = gdImageAlpha(src, pxl);
r = r + red;
g = g + green;
b = b + blue;
a = a + alpha;
r = (r > 255)? 255 : ((r < 0)? 0 : r);
g = (g > 255)? 255 : ((g < 0)? 0 : g);
b = (b > 255)? 255 : ((b < 0)? 0 : b);
a = (a > 127)? 127 : ((a < 0)? 0 : a);
new_pxl = gdImageColorAllocateAlpha(src, r, g, b, a);
if (new_pxl == -1) {
new_pxl = gdImageColorClosestAlpha(src, r, g, b, a);
}
gdImageSetPixel (src, x, y, new_pxl);
}
}
return 1;
}
/**
* Function: gdImageConvolution
*
* Apply a convolution matrix to an image
*
* Depending on the matrix a wide range of effects can be accomplished, e.g.
* blurring, sharpening, embossing and edge detection.
*
* Parameters:
* src - The image.
* filter - The 3x3 convolution matrix.
* filter_div - The value to divide the convoluted channel values by.
* offset - The value to add to the convoluted channel values.
*
* Returns:
* Non-zero on success, zero on failure.
*
* See also:
* - <gdImageEdgeDetectQuick>
* - <gdImageGaussianBlur>
* - <gdImageEmboss>
* - <gdImageMeanRemoval>
* - <gdImageSmooth>
*/
BGD_DECLARE(int) gdImageConvolution(gdImagePtr src, float filter[3][3], float filter_div, float offset)
{
int x, y, i, j, new_a;
float new_r, new_g, new_b;
int new_pxl, pxl=0;
gdImagePtr srcback;
FuncPtr f;
if (src==NULL) {
return 0;
}
/* We need the orinal image with each safe neoghb. pixel */
srcback = gdImageCreateTrueColor (src->sx, src->sy);
if (srcback==NULL) {
return 0;
}
gdImageSaveAlpha(srcback, 1);
new_pxl = gdImageColorAllocateAlpha(srcback, 0, 0, 0, 127);
gdImageFill(srcback, 0, 0, new_pxl);
gdImageCopy(srcback, src,0,0,0,0,src->sx,src->sy);
f = GET_PIXEL_FUNCTION(src);
for ( y=0; y<src->sy; y++) {
for(x=0; x<src->sx; x++) {
new_r = new_g = new_b = 0;
pxl = f(srcback, x, y);
new_a = gdImageAlpha(srcback, pxl);
for (j=0; j<3; j++) {
int yv = MIN(MAX(y - 1 + j, 0), src->sy - 1);
for (i=0; i<3; i++) {
pxl = f(srcback, MIN(MAX(x - 1 + i, 0), src->sx - 1), yv);
new_r += (float)gdImageRed(srcback, pxl) * filter[j][i];
new_g += (float)gdImageGreen(srcback, pxl) * filter[j][i];
new_b += (float)gdImageBlue(srcback, pxl) * filter[j][i];
}
}
new_r = (new_r/filter_div)+offset;
new_g = (new_g/filter_div)+offset;
new_b = (new_b/filter_div)+offset;
new_r = (new_r > 255.0f)? 255.0f : ((new_r < 0.0f)? 0.0f:new_r);
new_g = (new_g > 255.0f)? 255.0f : ((new_g < 0.0f)? 0.0f:new_g);
new_b = (new_b > 255.0f)? 255.0f : ((new_b < 0.0f)? 0.0f:new_b);
new_pxl = gdImageColorAllocateAlpha(src, (int)new_r, (int)new_g, (int)new_b, new_a);
if (new_pxl == -1) {
new_pxl = gdImageColorClosestAlpha(src, (int)new_r, (int)new_g, (int)new_b, new_a);
}
gdImageSetPixel (src, x, y, new_pxl);
}
}
gdImageDestroy(srcback);
return 1;
}
/*
Function: gdImageSelectiveBlur
*/
BGD_DECLARE(int) gdImageSelectiveBlur( gdImagePtr src)
{
int x, y, i, j;
float new_r, new_g, new_b;
int new_pxl, cpxl, pxl, new_a=0;
float flt_r [3][3];
float flt_g [3][3];
float flt_b [3][3];
float flt_r_sum, flt_g_sum, flt_b_sum;
gdImagePtr srcback;
FuncPtr f;
if (src==NULL) {
return 0;
}
/* We need the orinal image with each safe neoghb. pixel */
srcback = gdImageCreateTrueColor (src->sx, src->sy);
if (srcback==NULL) {
return 0;
}
gdImageCopy(srcback, src,0,0,0,0,src->sx,src->sy);
f = GET_PIXEL_FUNCTION(src);
for(y = 0; y<src->sy; y++) {
for (x=0; x<src->sx; x++) {
flt_r_sum = flt_g_sum = flt_b_sum = 0.0;
cpxl = f(src, x, y);
for (j=0; j<3; j++) {
for (i=0; i<3; i++) {
if ((j == 1) && (i == 1)) {
flt_r[1][1] = flt_g[1][1] = flt_b[1][1] = 0.5;
} else {
pxl = f(src, x-(3>>1)+i, y-(3>>1)+j);
new_a = gdImageAlpha(srcback, pxl);
new_r = ((float)gdImageRed(srcback, cpxl)) - ((float)gdImageRed (srcback, pxl));
if (new_r < 0.0f) {
new_r = -new_r;
}
if (new_r != 0) {
flt_r[j][i] = 1.0f/new_r;
} else {
flt_r[j][i] = 1.0f;
}
new_g = ((float)gdImageGreen(srcback, cpxl)) - ((float)gdImageGreen(srcback, pxl));
if (new_g < 0.0f) {
new_g = -new_g;
}
if (new_g != 0) {
flt_g[j][i] = 1.0f/new_g;
} else {
flt_g[j][i] = 1.0f;
}
new_b = ((float)gdImageBlue(srcback, cpxl)) - ((float)gdImageBlue(srcback, pxl));
if (new_b < 0.0f) {
new_b = -new_b;
}
if (new_b != 0) {
flt_b[j][i] = 1.0f/new_b;
} else {
flt_b[j][i] = 1.0f;
}
}
flt_r_sum += flt_r[j][i];
flt_g_sum += flt_g[j][i];
flt_b_sum += flt_b [j][i];
}
}
for (j=0; j<3; j++) {
for (i=0; i<3; i++) {
if (flt_r_sum != 0.0) {
flt_r[j][i] /= flt_r_sum;
}
if (flt_g_sum != 0.0) {
flt_g[j][i] /= flt_g_sum;
}
if (flt_b_sum != 0.0) {
flt_b [j][i] /= flt_b_sum;
}
}
}
new_r = new_g = new_b = 0.0;
for (j=0; j<3; j++) {
for (i=0; i<3; i++) {
pxl = f(src, x-(3>>1)+i, y-(3>>1)+j);
new_r += (float)gdImageRed(srcback, pxl) * flt_r[j][i];
new_g += (float)gdImageGreen(srcback, pxl) * flt_g[j][i];
new_b += (float)gdImageBlue(srcback, pxl) * flt_b[j][i];
}
}
new_r = (new_r > 255.0f)? 255.0f : ((new_r < 0.0f)? 0.0f:new_r);
new_g = (new_g > 255.0f)? 255.0f : ((new_g < 0.0f)? 0.0f:new_g);
new_b = (new_b > 255.0f)? 255.0f : ((new_b < 0.0f)? 0.0f:new_b);
new_pxl = gdImageColorAllocateAlpha(src, (int)new_r, (int)new_g, (int)new_b, new_a);
if (new_pxl == -1) {
new_pxl = gdImageColorClosestAlpha(src, (int)new_r, (int)new_g, (int)new_b, new_a);
}
gdImageSetPixel (src, x, y, new_pxl);
}
}
gdImageDestroy(srcback);
return 1;
}
/**
* Function: gdImageEdgeDetectQuick
*
* Edge detection of an image
*
* (see edge_detect_quick.jpg)
*
* Parameters:
* src - The image.
*
* Returns:
* Non-zero on success, zero on failure.
*
* See also:
* - <gdImageMeanRemoval>
* - <gdImageConvolution>
*/
BGD_DECLARE(int) gdImageEdgeDetectQuick(gdImagePtr src)
{
float filter[3][3] = {{-1.0,0.0,-1.0},
{0.0,4.0,0.0},
{-1.0,0.0,-1.0}};
return gdImageConvolution(src, filter, 1, 127);
}
/*
Function: gdImageGaussianBlur
<gdImageGaussianBlur> performs a Gaussian blur of radius 1 on the
image. The image is modified in place.
*NOTE:* You will almost certain want to use
<gdImageCopyGaussianBlurred> instead, as it allows you to change
your kernel size and sigma value. Future versions of this
function may fall back to calling it instead of
<gdImageConvolution>, causing subtle changes so be warned.
Parameters:
im - The image to blur
Returns:
GD_TRUE (1) on success, GD_FALSE (0) on failure.
*/
BGD_DECLARE(int) gdImageGaussianBlur(gdImagePtr im)
{
float filter[3][3] = {
{1.0, 2.0, 1.0},
{2.0, 4.0, 2.0},
{1.0, 2.0, 1.0}
};
return gdImageConvolution(im, filter, 16, 0);
}
/**
* Function: gdImageEmboss
*
* Emboss an image
*
* (see emboss.jpg)
*
* Parameters:
* im - The image.
*
* Returns:
* Non-zero on success, zero on failure.
*
* See also:
* - <gdImageConvolution>
*/
BGD_DECLARE(int) gdImageEmboss(gdImagePtr im)
{
/*
float filter[3][3] = {{1.0,1.0,1.0},
{0.0,0.0,0.0},
{-1.0,-1.0,-1.0}};
*/
float filter[3][3] = {{ 1.5, 0.0, 0.0},
{ 0.0, 0.0, 0.0},
{ 0.0, 0.0,-1.5}};
return gdImageConvolution(im, filter, 1, 127);
}
/**
* Function: gdImageMeanRemoval
*
* Mean removal of an image
*
* (see mean_removal.jpg)
*
* Parameters:
* im - The image.
*
* Returns:
* Non-zero on success, zero on failure.
*
* See also:
* - <gdImageEdgeDetectQuick>
* - <gdImageConvolution>
*/
BGD_DECLARE(int) gdImageMeanRemoval(gdImagePtr im)
{
float filter[3][3] = {{-1.0,-1.0,-1.0},
{-1.0,9.0,-1.0},
{-1.0,-1.0,-1.0}};
return gdImageConvolution(im, filter, 1, 0);
}
/**
* Function: gdImageSmooth
*
* Smooth an image
*
* (see smooth.jpg)
*
* Parameters:
* im - The image.
* weight - The strength of the smoothing.
*
* Returns:
* Non-zero on success, zero on failure.
*
* See also:
* - <gdImageConvolution>
*/
BGD_DECLARE(int) gdImageSmooth(gdImagePtr im, float weight)
{
float filter[3][3] = {{1.0,1.0,1.0},
{1.0,0.0,1.0},
{1.0,1.0,1.0}};
filter[1][1] = weight;
return gdImageConvolution(im, filter, weight+8, 0);
}
/* ======================== Gaussian Blur Code ======================== */
/* Return an array of coefficients for 'radius' and 'sigma' (sigma >=
* 0 means compute it). Result length is 2*radius+1. */
static double *
gaussian_coeffs(int radius, double sigmaArg) {
const double sigma = (sigmaArg <= 0.0) ? (2.0/3.0)*radius : sigmaArg;
const double s = 2.0 * sigma * sigma;
double *result;
double sum = 0;
int x, n, count;
count = 2*radius + 1;
result = gdMalloc(sizeof(double) * count);
if (!result) {
return NULL;
}/* if */
for (x = -radius; x <= radius; x++) {
double coeff = exp(-(x*x)/s);
sum += coeff;
result[x + radius] = coeff;
}/* for */
for (n = 0; n < count; n++) {
result[n] /= sum;
}/* for */
return result;
}/* gaussian_coeffs*/
static inline int
reflect(int max, int x)
{
assert(x > -max && x < 2*max);
if(x < 0) return -x;
if(x >= max) return max - (x - max) - 1;
return x;
}/* reflect*/
static inline void
applyCoeffsLine(gdImagePtr src, gdImagePtr dst, int line, int linelen,
double *coeffs, int radius, gdAxis axis)
{
int ndx;
for (ndx = 0; ndx < linelen; ndx++) {
double r = 0, g = 0, b = 0, a = 0;
int cndx;
int *dest = (axis == HORIZONTAL) ?
&dst->tpixels[line][ndx] :
&dst->tpixels[ndx][line];
for (cndx = -radius; cndx <= radius; cndx++) {
const double coeff = coeffs[cndx + radius];
const int rndx = reflect(linelen, ndx + cndx);
const int srcpx = (axis == HORIZONTAL) ?
src->tpixels[line][rndx] :
src->tpixels[rndx][line];
r += coeff * (double)gdTrueColorGetRed(srcpx);
g += coeff * (double)gdTrueColorGetGreen(srcpx);
b += coeff * (double)gdTrueColorGetBlue(srcpx);
a += coeff * (double)gdTrueColorGetAlpha(srcpx);
}/* for */
*dest = gdTrueColorAlpha(uchar_clamp(r, 0xFF), uchar_clamp(g, 0xFF),
uchar_clamp(b, 0xFF), uchar_clamp(a, 0x7F));
}/* for */
}/* applyCoeffsLine*/
static void
applyCoeffs(gdImagePtr src, gdImagePtr dst, double *coeffs, int radius,
gdAxis axis)
{
int line, numlines, linelen;
if (axis == HORIZONTAL) {
numlines = src->sy;
linelen = src->sx;
} else {
numlines = src->sx;
linelen = src->sy;
}/* if .. else*/
for (line = 0; line < numlines; line++) {
applyCoeffsLine(src, dst, line, linelen, coeffs, radius, axis);
}/* for */
}/* applyCoeffs*/
/*
Function: gdImageCopyGaussianBlurred
Return a copy of the source image _src_ blurred according to the
parameters using the Gaussian Blur algorithm.
_radius_ is a radius, not a diameter so a radius of 2 (for
example) will blur across a region 5 pixels across (2 to the
center, 1 for the center itself and another 2 to the other edge).
_sigma_ represents the "fatness" of the curve (lower == fatter).
If _sigma_ is less than or equal to 0,
<gdImageCopyGaussianBlurred> ignores it and instead computes an
"optimal" value. Be warned that future versions of this function
may compute sigma differently.
The resulting image is always truecolor.
More Details:
A Gaussian Blur is generated by replacing each pixel's color
values with the average of the surrounding pixels' colors. This
region is a circle whose radius is given by argument _radius_.
Thus, a larger radius will yield a blurrier image.
This average is not a simple mean of the values. Instead, values
are weighted using the Gaussian function (roughly a bell curve
centered around the destination pixel) giving it much more
influence on the result than its neighbours. Thus, a fatter curve
will give the center pixel more weight and make the image less
blurry; lower _sigma_ values will yield flatter curves.
Currently, <gdImageCopyGaussianBlurred> computes the default sigma
as
(2/3)*radius
Note, however that we reserve the right to change this if we find
a better ratio. If you absolutely need the current sigma value,
you should set it yourself.
Parameters:
src - the source image
radius - the blur radius (*not* diameter--range is 2*radius + 1)
sigma - the sigma value or a value <= 0.0 to use the computed default
Returns:
The new image or NULL if an error occurred. The result is always
truecolor.
Example:
(start code)
FILE *in;
gdImagePtr result, src;
in = fopen("foo.png", "rb");
src = gdImageCreateFromPng(in);
result = gdImageCopyGaussianBlurred(im, src->sx / 10, -1.0);
(end code)
*/
/* TODO: Look into turning this into a generic seperable filter
* function with Gaussian Blur being one special case. (At the
* moment, I can't find any other useful separable filter so for not,
* it's just blur.) */
BGD_DECLARE(gdImagePtr)
gdImageCopyGaussianBlurred(gdImagePtr src, int radius, double sigma)
{
gdImagePtr tmp = NULL, result = NULL;
double *coeffs;
int freeSrc = 0;
if (radius < 1) {
return NULL;
}/* if */
/* Compute the coefficients. */
coeffs = gaussian_coeffs(radius, sigma);
if (!coeffs) {
return NULL;
}/* if */
/* If the image is not truecolor, we first make a truecolor
* scratch copy. */
if (!src->trueColor) {
int tcstat;
src = gdImageClone(src);
if (!src) {
gdFree(coeffs);
return NULL;
}
tcstat = gdImagePaletteToTrueColor(src);
if (!tcstat) {
gdImageDestroy(src);
gdFree(coeffs);
return NULL;
}/* if */
freeSrc = 1;
}/* if */
/* Apply the filter horizontally. */
tmp = gdImageCreateTrueColor(src->sx, src->sy);
if (!tmp) {
gdFree(coeffs);
return NULL;
}
applyCoeffs(src, tmp, coeffs, radius, HORIZONTAL);
/* Apply the filter vertically. */
result = gdImageCreateTrueColor(src->sx, src->sy);
if (result) {
applyCoeffs(tmp, result, coeffs, radius, VERTICAL);
}/* if */
gdImageDestroy(tmp);
gdFree(coeffs);
if (freeSrc) gdImageDestroy(src);
return result;
}/* gdImageCopyGaussianBlurred*/
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