如何使用Matlab将辣椒图像中的绿色像素更改为金色？

Question

I want to change green color pixels to gold color in peppers.png image in Matlab. How can I do this task? Thanks very much for your help

Answer 1

Introduction

Using the HSV colorspace gives a better intuition of detecting a certain color hue and manipulating it. For further information, read the following answer .

Solution

Given an image in hsv format, each color has a certain range which it can reside in. In the peppers image, the hue channel of green peppers is in the range [40/360,180/360] (more or less). Also, the color gold can be identified by a hue value of 0.125 and 'V' value of 0.8. Therefore, a good way to change green to gold in a certain picture will be as follows:

1. transform the image to hsv.
2. locate green colors by identifying hue value between the range [40/360,180/360].
3. changing their first channel to 0.125, and their second channel to 0.8.
4. transform back to rgb.

*comment: instead of fully changing the third channel of the green pixels to 0.8, it will be better to perform an averaging of 0.8 with the originally stored value, to get a more natural effect (see code below).

Code

%reads the image. converts it to hsv.
I = imread('peppers.png');
hsv = rgb2hsv(I);

%locate pixels with green color
GREEN_RANGE = [40,180]/360;
greenAreasMask = hsv(:,:,1)>GREEN_RANGE(1) & hsv(:,:,1) < GREEN_RANGE(2);

%change their hue value to 0.125
HUE_FOR_GOLD = 0.12;
V_FOR_GOLD = 0.8;
goldHsv1 = hsv(:,:,1);
goldHsv1(greenAreasMask)=HUE_FOR_GOLD;
goldHsv3 = hsv(:,:,3);
goldHsv3(greenAreasMask)=V_FOR_GOLD;
newHsv = hsv;
newHsv(:,:,1) = goldHsv1;
newHsv(:,:,3) = newHsv(:,:,3) + goldHsv3 / 2;
%transform back to RGB
res = hsv2rgb(newHsv);

Result

As you can see, the green pixels became more goldish. There is a room for improvement, but I think that this would be a good start for you. To improve the result you can modify the green and gold HSV values, and use morphological operations on greenAreasMask.