I have an image that I import into Octave 5.2, and I would like to create an outline all the way around the image array using RGB values.
I'm having trouble inserting the RGB values back into the array correctly, inserting / generating the two rows at top, two columns on the left, two columns on the right, and two rows on the bottom all the way around the image / converted double array.
Example of original image:
Example of the image I'm trying to get when done:
My logic was:
To convert the image to a double array so I can do math / insert the RGB values where I wanted them.
Insert the RGB values into the left, right, top, bottom of the array.
Convert the double array back to uint8 to export / view it as image.
My code so far:
pkg load image
img_fn=('https://i.imgur.com/KKxJaOy.png'); %original image
f=imread(img_fn);
[im_r im_c]=size(f);
size_min=min(im_r,im_c); %get minum size from row and col
f_double=double(f); %need to convert to double to do math functions on it
outline_left_of_box=repmat(255,[rows(f_double),2]); %Create left line array of outline red box
f_double_tmp_red(:,:,1)=[outline_left_of_box,f_double];%Create left line of outline red box
red_outline_right_of_box=repmat(255,[rows(f_double),2]); %Create right line array of outline red box
red_outline_top_of_box=repmat(255,[2,columns(f_double)]); %Create top line array of outline red box
red_outline_bottom_of_box=repmat(255,[2,columns(f_double)]); %Create bottom line array of outline red box
%convert back to image
red_outline_img=uint8(f_double);
imshow(red_outline_img); %used to show image in octave plot window
Please note: I'm converting the image array into a double because calculations will be done on the array to get the desired color box around the image, but I'm just trying to get the inserting RGB values into the array issue fixed first.
Maybe it's easier to simply paste the inner part of the input image onto some "background" image with the desired border color, like so:
pkg load image
% Read image, get dimensions, convert to double
f = imread('https://i.imgur.com/KKxJaOy.png');
[im_ro, im_co, im_ch] = size(f);
f_double = double(f);
% Set up width and color of border
bw = 2;
color = ones(1, 1, im_ch);
color(1, 1, :) = [255, 0, 0];
% Create image of same size as input with solid color, and paste inner part of input
red_outline_img = ones(im_ro, im_co, im_ch) .* color;
red_outline_img(bw+1:end-bw, bw+1:end-bw, :) = f_double(bw+1:end-bw, bw+1:end-bw, :);
red_outline_img = uint8(red_outline_img);
imshow(red_outline_img);
That'd be the output:
Another thing you could try is plot the lines as you suggest, which can be done very efficiently with some clever use of xlim/ylim, and then print the whole thing as an -RGBImage to get it back in image form.
The only caveat here though is that you will need to play with the formatting options to get what you're really after (e.g. in case you want higher or lower resolution), since you really are printing what's on your screen at this point.
E.g.
L = imread('leaf.png');
imshow(L)
hold on
plot( [xlim, fliplr(xlim);xlim, xlim], [ylim, ylim;fliplr(ylim), ylim], 'r', 'linewidth', 2 )
hold off
set( gca, 'position', [0, 0, 1, 1] );
set( gcf, 'paperposition', [0, 0, 1, 1] );
R = print( '-RGBImage' );
close
imshow(R); set( gcf, 'color', 'k'); axis off
Is it possible that we assign colour for different series ?
I would like to assign the colour to the series
1H = Blue
1L = Red
PV = Black
Thanks.
I am creating an application in win32 api, which will use a progress bar. This progress bar, should change its color. From red (left end) to green(right), and in the middle some yellow.
I searched a little, and found out, that I should use HSV to achieve this. I just don't know how? I found in this link, two functions, to convert the color, from RGB to HSV and back.
But what should I do if the color has been converted to HSV?
Like RGB coordinates, HSV coordinates define a point in a three dimensional space.
You may find a trajectory form one point (x0, one color) to the second (x1) with a formula like:
x = x0 + alpha * (x1-x0)
with alpha varying form 0.0 to 1.0
You can do this for all three components simultaneaously.
With a trajectory from green to red in HSV space you will mainly modify the H (Hue) value. If you want to see some yellow in the middle of your path (and not violett) you need to define a second or even third color and walk
green -> yellow -> red
Edit: Example
int hue0 = 0; // red
int hue2 = 120; // green
// find 100 colors between red and green
for(double alpha = 0; alpha <= 1.0; alpha += 0.01)
{
hueX = hue0 + alpha * (hue1 - hue0);
// same for value, saturation:
// valX = val0 + alpha * (val1 - val0)
// ...
// plot this color
}
Say you want to put pixel with a color (R0 G200 B255) in a BMP picture and you have transp option in percents.
How do I determine the new pixel color, considering the transp and the background color?
I actually could figure out a formula that looks promising:
newpixel = newpixel + (bgpixel * transp) / %(transp of 255)
I created it by analyzing the pixel color change in GIMP. Not sure if that is the correct formula. I think it is also rounded up.
The standard formula is pixel = new_pixel * alpha + pixel * (1 - alpha), where alpha is a number between 0 and 1 that describes the opacity of the new (foreground) pixel.
You'll note that if the new pixel is fully transparent (alpha = 0) the pixel is unchanged and that if the new pixel is fully opaque (alpha = 1) the new pixel replaces the old one.
This formula must be applied separately for each pixel components (red, green and blue).
the code needs to change to 24 bit pixels.
where the 4th byte is the transparency factor.
The actual color values do not change
I have a one ambient light with intesity ( 10000,10000, 5000 ). I am trying to color the primitive.
As you know, color values for R,G, and B are between 0 and 255. How can I find color of the pixel according to light intesity ?
platform : linux and programming language c
EDIT :
In ray tracer, we are calculating
for each ambient light in the environment
color . R += Intensity of the light * ambient coefficient for color R
color . G += Intensity of the light * ambient coefficient for color G
color . B += Intensity of the light * ambient coefficient for color B
However, whenever I have tried to emit this pixel color value on the screen with openGL.
set pixel color ( color )
I have taken wrong color because of intensity is high and maximum color value is low.
The question is unclear, as written, so here's some general advice.
Colours in renderers are typically held as values with a nominal range of [0..1] for each of the RGB components.
When those colours are rendered to pixels, they're usually just multiplied by 255 to give a 24-bit colour value (8 bits per component).
If the original values are outside of the [0..1] range they must be "clamped" so that the resulting pixel values fall in the [0..255] range.
That clamping can either be done "per component", which in your case would result in (255, 255, 255), or each component could be divided by the maximum component, giving (255, 255, 127) - i.e. preserving their relative intensities in pseudo-code:
float scale = max(r, g, b);
if (scale < 1) {
scale = 1; // don't normalise colours that are "in range"
}
byte R = 255 * (r < 0 ? 0 : r / scale);
byte G = 255 * (g < 0 ? 0 : g / scale);
byte B = 255 * (b < 0 ? 0 : b / scale);
It's usual for all intermediate calculations to preserve the full dynamic range of intensities. For example, it wouldn't make sense for the Sun to have a brightness of "1", since every other object in the scene would by comparison have an almost infinitesimally small value.
The net result of the clamping will therefore be that light sources which contribute too much light to the scene will produce "saturation" of the image - i.e. the same effect that you get if you leave the shutter open too long on a picture of a bright scene.
It's this one you want:
brightness = sqrt( .241*R*R + .691*G*G + .068*B*B )
Find more here: http://www.nbdtech.com/Blog/archive/2008/04/27/Calculating-the-Perceived-Brightness-of-a-Color.aspx
or here: http://en.wikipedia.org/wiki/Luminance_(relative)