Clive,
Can you give more details about this Ben Day dots filter Algorithm please?
Who wrote it, which libraries it uses, about the program it's a part of,
etc - anything usefull to assist in making use of it.
James.
Clive McCarthy DIWOed on the 7th of February:
/*-----------------------------------------------------------------------------
This filter emulates Ben Day dots
Benjamin Henry Day 1810-89, American journalist.
He learned the printer's trade in the office of the Springfield (Mass.)
Republican and opened a printing office in New York City.
Lack of work during a financial depression led him to begin publishing
(1833) the New York Sun.
In 1842, Day founded the monthly Brother Jonathan,
which later became the first illustrated weekly in the United States.
His son Benjamin (1838-1916) invented the Ben Day process for shading
printed illustrations
generate a 4,800 wide image with 60 dots -- each is 80 pixels in diameter
-----------------------------------------------------------------------------*/
void ben_day_filter(TIFFIMAGEACCESS *poster)
{
TIFFIMAGEACCESS *ben_day;
char ben_day_filename[MAXPATH];
unsigned long x, y, x_out, y_out;
int i, j, x_offset, y_offset;
int dot_radius, box_radius, dot_radius_squared, radius_squared;
int pitch, row, radius, diameter;
unsigned char r, g, b, r_bakg, g_bakg, b_bakg;
double r_sum, g_sum, b_sum, scale;
double hue, sat, lit;
char *poster_pixel_ptr, *ben_day_pixel_ptr;
// set the radius so that there are ~90 dots across the image
radius = poster->image_width / 180;
if(radius < 10) radius = 10;
pitch = radius * sqrt(3.0);
diameter = (2 * radius) + 1; // the center is the zero-th pixel
if(global_image_width == 0)
{
scale = 1.0; }
else
{
scale = (double)global_image_width / poster->image_width;
}
//printf("Ben Day dot Y pitch = %2d Y excess = %2d\n",
(poster->image_width % diameter), (poster->image_length % diameter));
//printf("Ben Day dot X diameter = %2d Y pitch = %2d\n", diameter,
pitch);
printf("Ben Day radius %2d ...", radius);
if(radius < 4)
{
printf("image width (%d pixels) is too small for Ben Day dots\n",
poster->image_width);
xexit(1);
}
x_offset = (poster->image_width % diameter) / 2;
//y_offset = (poster->image_length % pitch) / 2;
y_offset = ((poster->image_length - diameter) % pitch) / 2;
printf("Ben Day dot X excess = %2d Y excess = %2d\n",
(poster->image_width % diameter), (poster->image_length % diameter));
printf("Ben Day dot X offset = %2d Y offset = %2d\n", x_offset,
y_offset);
prefix_long_filename("Ben_Day", poster->filename, ben_day_filename);
dots_per_inch = 100; // set the dpi for Ben Day printing
ben_day = tifio_open_write
(
ben_day_filename,
poster->image_width * scale,
poster->image_length * scale,
CHANNELS_RGBA, // open with an alpha channel
BUFFERED
);
tifio_initialize_buffer_value(ben_day, 0); // black and transparent
for(y = radius + y_offset, row = 0; y < poster->image_length - radius; y
+= pitch, row++)
{
// inset on even/odd rows
for(x = radius + x_offset + radius * (row%2); x < poster->image_width -
radius; x += diameter)
{
// average the region
r_sum = 0; g_sum = 0; b_sum = 0;
for(i = -radius; i <= radius; i++)
{
for(j = -radius; j <= radius; j++)
{
poster_pixel_ptr = PIXEL_BUFFER_PTR(poster->image_buffer,
poster->image_width, (x + i), (y + j));
PTR_to_RGB(poster_pixel_ptr, r, g, b);
r_sum += r; g_sum += g; b_sum += b;
}
}
r = r_sum / (diameter) / (diameter);
g = g_sum / (diameter) / (diameter);
b = b_sum / (diameter) / (diameter);
RGBtoHSL(r, g, b, &hue, &sat, &lit);
dot_radius = ((radius * scale) - 1) * (1.0 - lit);
sat = 0.90; // not too saturated
HSLtoRGB(hue, sat, lit, &r, &g, &b);
/*
if(TRUE || lit > 0.5)
{
// colored dot on a white background
dot_radius = ((radius * scale) - 1) * (1.0 - lit);
//lit = 0.5;
sat = 0.90; // not too saturated
HSLtoRGB(hue, sat, lit, &r, &g, &b);
r_bakg = 255; g_bakg = 255; b_bakg = 255;
}
else
{
// white dot on a colored background
dot_radius = (radius) * (1.0 - lit);
lit = 0.5;
sat = 0.80; // not too saturated
HSLtoRGB(hue, sat, lit, &r_bakg, &g_bakg, &b_bakg);
r = 255; g = 255; b = 255;
}
*/
dot_radius_squared = dot_radius * dot_radius;
x_out = scale * x;
y_out = scale * y;
// a square box of pixels is colored
box_radius = dot_radius + 2;
for(i = -box_radius; i <= box_radius; i++)
{
for(j = -box_radius; j <= box_radius; j++)
{
ben_day_pixel_ptr = PIXEL_RGBA_BUFFER_PTR(ben_day->image_buffer,
ben_day->image_width, ben_day->channels, (x_out + i), (y_out + j));
RGB_to_PTR(r, g, b, ben_day_pixel_ptr);
}
}
for(i = -dot_radius; i <= dot_radius && (dot_radius != 0); i++)
{
for(j = -dot_radius; j <= dot_radius; j++)
{
// a square box of pixels is colored
ben_day_pixel_ptr = PIXEL_RGBA_BUFFER_PTR(ben_day->image_buffer,
ben_day->image_width, ben_day->channels, (x_out + i), (y_out + j));
RGB_to_PTR(r, g, b, ben_day_pixel_ptr);
if((i * i + j * j) <= dot_radius_squared)
{
// the dot alpha is 255 = opaque
ALPHA_to_PTR(255, ben_day_pixel_ptr);
}
else
{
// the background alpha is 0 = transparent
ALPHA_to_PTR(0, ben_day_pixel_ptr);
}
}
}
}
}
map_to_palette_file(ben_day, "Ben_Day.txt");
gaussian_alpha_sigma14_filter(ben_day);
//white_transparent_generate_alpha_from_rgb(ben_day);
//predictor_differencing(ben_day);
//predictor_de_differencing(ben_day);
sprintf(ben_day->description, "source image: %s Ben Day radius %d",
poster->filename, radius);
tifio_close(ben_day);
dots_per_inch = DEFAULT_DOTS_PER_INCH;
printf(" done\n");
}
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