There is a color difference in the non_stroking_color

[KaboChow]

Hi Team,
I am trying to use the following JS code to convert the obtained non_stoking.color into RGB color for use in HTML.
`

            if(fillColor.length===1){
                return 'rgb(' + (255*(1.0-fillColor[0])).toFixed(0) + ')';
            }
            
            if(fillColor.length===3){
                const r = 255 * fillColor[0];
                const g = 255 * fillColor[1];
                const b = 255 * fillColor[2];
                return 'rgb(' + r.toFixed(0) + ',' + g.toFixed(0) +',' + b.toFixed(0) + ')';
            }
           
            if(fillColor.length===4){
                const r = 255*(1.0-(fillColor[0]+fillColor[3]));
                const g = 255*(1.0-(fillColor[1]+fillColor[3]));
                const b = 255*(1.0-(fillColor[2]+fillColor[3]));
                return 'rgb(' + r.toFixed(0) + ',' + g.toFixed(0) +',' + b.toFixed(0) + ')';
            }

`

But there are obvious color differences in the obtained colors.
pdf:

html:

This is the PDF I used for testing:
TEST 5 - 48in-Height-Chef-Supplies-Banner-d4-ced6f345009972ad3e50309422be6654.pdf

Does anyone know how to solve it? thank you

[jsvine]

Given that this doesn't seem to be a bug in pdfplumber, I'm converting this to a discussion. The issue here seems to be that the colors are defined as CMYK instead of RGB(A). Plugging in the color values for the CHEF curves, you get a color that looks correct:

[KaboChow]

Hi! @jsvine, thank you for your reply!

You're right, when the curve uses the CMYK format, the color is normal!
I apologize for not fully expressing my question.

When the curve uses the RGB format, the value of non_stroking_color shows the following issues:

The correct color is purple, but the value is [1].
There are cases where negative values appear, such as [76.470588, -3, -8].
I am unable to distinguish whether non_stroking_color is using CMYK or RGB based on the limited information.

This is the PDF I used for testing:
TEST 62 - trouse-fd7b74be16be80f5c0397ef382664f74.pdf
TEST 66 - IE_Logo_Vector-2dc8c79f1cea26d809275d24b699b7c0.pdf

[mkl-public]

TEST 62 - trouse-fd7b74be16be80f5c0397ef382664f74.pdf: Here a Lab color space with three components is used. The latter two components may be negative.

TEST 66 - IE_Logo_Vector-2dc8c79f1cea26d809275d24b699b7c0.pdf: Here Separation color spaces with a single component are used.