CropBlackBands problem

[borquee]

Hi
I am testing GdTwain (lite version) and I have a problem with CropBlackBands

It just doesnt do anything with the picture (example is attached) I tried changing tresholds (0, 20, 50, 75...)

Before CropBlackBands I did CropBorders (which works nice)

I am working with VB6 and latest OCX from the webiste (well... from three days ago)

Thanks,
B

[Loïc]

Hi,

Your image is a true color image. The borders are not realy black, they are greyscale.

The CropBlackBands() & CropWhiteBands() methods are optimized to work with true Black and true White color in 1bpp bitmap.

For non indexed color bitmap, you need to use the CropBorders() method like you did

Best regards,

Loïc Carrère

[borquee]

Hi,
Thanks for your answer... but what is need for treshold parameter if it works with BW pictures only?

I am scanning with ADF and my scan was originaly greyscale 8bit, I mistakenly saved it as 24 bit.

CropBorders() fixed the problem with white border around image and that was great.. just I have to crop the blacks too ... any othere way (except manual crop)

Thanks,
B.

[borquee]

Hi again

CropBlackBands() works if scanner brightness is set to 0.

If brightness is set to 1 it will not work ... well... range of brightness setup is -1000 to 1000 so that value of 1 one should not realy make any difference since it's 8 bit and brightness of 1 should lift the black for about 1/2000 value (right?) and that's no change

Any ideas?

B.

[Loïc]

HI,

I' ve tried CropBorders() on your uploaded image with perfect result. Maybe you need to call this method two times ??

In fact, CropBlackBands() & CropWhiteBands() methods should be used only on 1 bpp image. These methods are checking only for full white RGB(255, 255, 255) or full Black RGB(0, 0, 0) colors.

Code: Select all

range of brightness setup is -1000 to 1000 so that value of 1 one should not realy make any difference since it's 8 bit and brightness of 1 should lift the black for about 1/2000 value (right?) and that's no change

It is another issue but I can say that:
- For index color bitmap it is not working like that. 8bpp image can handle only 256 different colors. Therefore 1/2000 range can't make any sense.
- For true color image it depend of your acquisition device. you can use the TwainGetCapRangeNumeric() method to cath the supported brightness values:

https://www.gdpicture.com/guides/gdpicture/v4/gdtwainp ... meric.html

Code: Select all

Dim bSuccess As Boolean
Dim nMinValue As Double, nMaxValue As Double, nStepValue As Double

bSuccess = Twain1.TwainGetCapRangeNumeric(ICAP_BRIGHTNESS, nMinValue, nMaxValue, nStepValue)

Best regards,

Loïc

[borquee]

Thank you for your answer.

[Loïc]

You are welcome !

Best regards,

Loïc