void NamedWindow::showImage3D(Halide::Image<uint8_t> im)
{
static Halide::Func convert("convertToMat3D");
static Halide::ImageParam ip(Halide::UInt(8), 3);
static Halide::Var x, y, c;
if (!convert.defined())
{
convert(c, x, y) = ip(x, y, 2 - c);
convert.vectorize(x, 4).parallel(y, 4);
}
ip.set(im);
cv::Mat mat(im.height(), im.width(), CV_8UC3, cv::Scalar(0));
convert.realize(Halide::Buffer(Halide::UInt(8), im.channels(), im.width(), im.height(), 0, mat.data));
cv::imshow(name, mat);
}
int main(int argc, char **argv) {
// This program defines a single-stage imaging pipeline that
// brightens an image.
// First we'll load the input image we wish to brighten.
Halide::Image<uint8_t> input = load<uint8_t>("../apps/images/rgb.png");
// Next we define our Func object that represents our one pipeline
// stage.
Halide::Func brighter;
// Our Func will have three arguments, representing the position
// in the image and the color channel. Halide treats color
// channels as an extra dimension of the image.
Halide::Var x, y, c;
// Normally we'd probably write the whole function definition on
// one line. Here we'll break it apart so we can explain what
// we're doing at every step.
// For each pixel of the input image.
Halide::Expr value = input(x, y, c);
// Cast it to a floating point value.
value = Halide::cast<float>(value);
// Multiply it by 1.5 to brighten it. Halide represents real
// numbers as floats, not doubles, so we stick an 'f' on the end
// of our constant.
value = value * 1.5f;
// Clamp it to be less than 255, so we don't get overflow when we
// cast it back to an 8-bit unsigned int.
value = Halide::min(value, 255.0f);
// Cast it back to an 8-bit unsigned integer.
value = Halide::cast<uint8_t>(value);
// Define the function.
brighter(x, y, c) = value;
// The equivalent one-liner to all of the above is:
//
// brighter(x, y, c) = Halide::cast<uint8_t>(min(input(x, y, c) * 1.5f, 255));
//
// In the shorter version:
// - I skipped the cast to float, because multiplying by 1.5f does
// that automatically.
// - I also used integer constants in clamp, because they get cast
// to match the type of the first argument.
// - I left the Halide:: off clamp. It's unnecessary due to Koenig
// lookup.
// Remember. All we've done so far is build a representation of a
// Halide program in memory. We haven't actually processed any
// pixels yet. We haven't even compiled that Halide program yet.
// So now we'll realize the Func. The size of the output image
// should match the size of the input image. If we just wanted to
// brighten a portion of the input image we could request a
// smaller size. If we request a larger size Halide will throw an
// error at runtime telling us we're trying to read out of bounds
// on the input image.
Halide::Image<uint8_t> output = brighter.realize(input.width(), input.height(), input.channels());
// Save the output for inspection. It should look like a bright parrot.
save(output, "brighter.png");
printf("Success!\n");
return 0;
}
