// KERNEL
// SUPPORTING FUNCTIONS
// Used by makeStrip (returns coord of pixel to be
sampled)
vec2 sampleHere(vec2 xy, float cellWidth, float
cellHeight, float cols)
{
// Calculate Row and Column for current iteration
float rowNum = ceil(xy.x / cols);
float colNum = xy.x - ((rowNum - 1.0) * cols);
// Calculate position of pixel to copy
xy.x = colNum * cellWidth;
xy.y = rowNum * cellHeight;
// Return coord for sampler
return xy;
}
// MAIN KERNEL FUNCTIONS (RETURN IMAGES)
// Pixellates image with exact dimensions for pixel
tiles' width and height
kernel vec4 xy_pixellate(sampler Image, float
CellWidth, float CellHeight)
{
// Current pixel location
vec2 xy = destCoord();
// Left and right of tile
float x1 = floor(xy.x / CellWidth) * CellWidth;
float x2 = (ceil(xy.x / CellWidth)) * CellWidth;
// Top and bottom of tile
float y1 = (floor(xy.y / CellHeight) * CellHeight);
float y2 = (ceil(xy.y / CellHeight)) * CellHeight;
// Average left and right pixels
vec4 avgX = (sample(Image, samplerTransform(Image,
vec2(x1, y1)))+(sample(Image,
samplerTransform(Image,
vec2(x2, y1))))) / 2.0;
// Average top and bottom pixels
vec4 avgY = (sample(Image, samplerTransform(Image,
vec2(x1, y1)))+(sample(Image,
samplerTransform(Image,
vec2(x1, y2))))) / 2.0;
// Centre pixel
vec4 avgC = sample(Image, samplerTransform(Image,
vec2(x1+(CellWidth/2.0), y2+(CellHeight/2.0))));
// Average the averages + centre
vec4 outPix = (avgX+avgY+avgC) / 3.0;
// Output
return outPix;
}
// Creates 1-pixel-high strip from input image
kernel vec4 makeStrip(sampler Image, float
CellWidth,
float CellHeight, float CellNum, float Cols)
{
// Current pixel position
vec2 xy = destCoord();
vec2 samplePos = (xy.x > CellNum) ? vec2(0.0,0.0) :
(xy.y > 10.0) ? vec2(0.0,0.0) : sampleHere(xy,
CellWidth, CellHeight, Cols);
// Output
return sample(Image, samplerTransform(Image,
vec2(samplePos)));
}
// JAVASCRIPT
function __image main(__image Image, __number Rows,
__number Cols)
{
// CREATE CONTROL VALUES
// Input image dimensions
var Width = Image.extent.width;
var Height = Image.extent.height;
// Dimensions of Pixellation cells
var CellWidth = Width / (Math.ceil(Rows));
var CellHeight = Height / (Math.ceil(Cols));
// Total number of cells
var CellNum = Rows * Cols;
// DOD rect
var dodRect = new Vec(0.0, 0.0, Width, Height);
// IMAGE OPERATIONS
// Pixellate image
imagePixellated = xy_pixellate.apply(dodRect, null,
Image, CellWidth, CellHeight);
// Create strip
imageStrip = makeStrip.apply(dodRect, null,
imagePixellated, CellWidth, CellHeight, CellNum,
Cols);
// Crop
imageCropped = Filter.Crop(imageStrip, new Vec(0.0,
0.0, CellNum, 1.0));
// Output
return imageCropped;
}
Anything obvious jump out as still being wrong?
Cheers again for your advice,
Alex
--- Kevin Quennesson <[EMAIL PROTECTED]> wrote:
Sure,
The ROI is the rectangle in the source image that
is
needed by the
kernel to process pixel in a given destination
rectangle (dstRect)
Here's a example of simple subsampling by 2 of an
image:
//KERNEL:
kernel vec4 susbample(sampler image)
{
vec2 xy = destCoord();
xy = (xy - vec2(0.5,0.5)) * 2. + vec2(0.5,0.5);
//
Pixels are
sampled at half coordinates.
return sample(image, samplerTransform(image,
xy));
}
//JavaScript:
function myROIFunction(samplerIndex, dstRect,
info)
{
var roiRect = new Vec(dstRect.x*2., dstRect.y*2.,
dstRect.width*2.,
dstRect.height*2.); //ROI is twice bigger than
dstRect
return roiRect;
}
susbample.ROIHandler = myROIFunction;
function __image main(__image image) {
var dodRect = new Vec(image.extent.x/2.,
image.extent.y/2.,
image.extent.width/2., image.extent.height/2.);
//DOD of resulting
image is twice smaller that image.extent
return susbample.apply(dodRect, null, image);
}
On Dec 11, 2007, at 12:48 AM, Alex Drinkwater
wrote:
On 11 Dec 2007, at 03:32, Kevin Quennesson
wrote:
Hi,
When your kernel reads pixel at a location
different from the
