Why the G color plane curve of four different groups of image plotted against another constant variables has different shape from its average value?

I have seven green colour images of different intensities at different spatial positions. i used four different positions to find out the difference in color plane results.the green color plane curve plotted against another constant variables of these images produce dissimilar curve shape(i.e. green color plane value differs when i change its position in x-axes). what could be the reason a same image has different green color plane value at different positions. the codes that i had used in this task is: a=0.85; for i=3:9 filename=strcat('D:\2nd year\EXP season 2\Dry\cat1\',num2str(i),'.bmp'); I=imread(filename); I1=I(:,:,2); I2=I(:,:,3); G_channel_cat1(i-2)=mean(mean(I1(293+(-5:5),250+(-5:5))))-mean(mean(I2(293+(-5:5),250+(-5:5))))*a; end

Answer 1

[Image Analyst]

I'm not sure what you're saying. It's like you're asking "How can different images have different values in the green channel?" But that can't be it because the answer to that is obvious. So can you rephrase what you're asking and perhaps upload some images, diagrams, plots, screenshots, code, or anything else that might help illustrate your situation? Also explain exactly what are "the other constant variables".

[satish thapaliya]

actually its the G channel curve against IgE concentration that i want to plot form images of the allergen cards used in ELISA reaction. i had seven different serum sample(with differen antibody concentration) so it produced seven different colored products. I used the images of those color product to obtain G channel value and as i had already known the antibody(IgE) concentration i plotted the curve by using G channel value against IgE concentration. i used the same seven images again in another group in different position to get the g channel value but the result was different. i repeated the process four times and plotted four different curves but the curve shape was not similar and the shape of curve obtained by using average G channel value(for seven images) from four groups was also not similar. What may be the cause? the whole code for four groups(with images i=3:9) was

a=0.85; for i=3:9 filename=strcat('D:\2nd year\EXP season 2\Dry\cat1\',num2str(i),'.bmp'); I=imread(filename); I1=I(:,:,2); I2=I(:,:,3); G_channel_cat1(i-2)=mean(mean(I1(293+(-5:5),250+(-5:5))))-mean(mean(I2(293+(-5:5),250+(-5:5))))*a; end for i=3:9 filename=strcat('D:\2nd year\EXP season 2\Dry\cat2\',num2str(i),'.bmp'); I=imread(filename); I1=I(:,:,2); I2=I(:,:,3); G_channel_cat2(i-2)=mean(mean(I1(301+(-5:5),250+(-5:5))))-mean(mean(I2(301+(-5:5),250+(-5:5))))*a; end for i=3:9 filename=strcat('D:\2nd year\EXP season 2\Dry\cat3\',num2str(i),'.bmp'); I=imread(filename); I1=I(:,:,2); I2=I(:,:,3); G_channel_cat3(i-2)=mean(mean(I1(310+(-5:5),250+(-5:5))))-mean(mean(I2(310+(-5:5),250+(-5:5))))*a; end for i=3:9 filename=strcat('D:\2nd year\EXP season 2\Dry\cat4\',num2str(i),'.bmp'); I=imread(filename); I1=I(:,:,2); I2=I(:,:,3); G_channel_cat4(i-2)=mean(mean(I1(316+(-5:5),250+(-5:5))))-mean(mean(I2(316+(-5:5),250+(-5:5))))*a; end x=[0.121,0.422,0.844,4.219,12.053,21.094,60.267]; for i=1:7 y(i)=(G_channel_cat1(i)+G_channel_cat2(i)+G_channel_cat3(i)+G_channel_cat4(i))/4; end plot(y,x,'r')

[Image Analyst]

OK, so you're plotting the average green color value from an image versus the known IgE concentration. And you expect to see a relationship. OK fine. But I don't know what this means " i used the same seven images again in another group in different position ". Do you mean that you just looked at a different group of images, and in a different place (pixel location) in those images to measure the mean green value?

[satish thapaliya]

no the images were same but the pixel location was shifted by equal distance in every preceding group. I think the value of G channel should be same irrespective to image location but it was not so.

[Image Analyst]

Again, a picture would be helpful. Also outline the regions of interest so we can see what you're looking at.

[satish thapaliya]

I don't know how could I upload the image here?