Encode Jpeg by IJL

[yasu]

Hi,

I'm trying to encode YCbCr422(DIB) to JPEG by using IJL without converting it to 24-bits RGB image. However, the create JPEG image darkens compared with original image.

jCprops.DIBWidth = Wid;
jCprops.DIBHeight = Hei*(-1);
jCprops.DIBBytes = pYCbCr;
jCprops.DIBPadBytes = 0;
jCprops.DIBChannels = 3;
jCprops.DIBColor = IJL_YCBCR;
jCprops.DIBSubsampling = IJL_422;

jCprops.JPGWidth = Wid;
jCprops.JPGHeight = Hei;
jCprops.JPGChannels = 3;
jCprops.JPGColor = IJL_YCBCR;
jCprops.JPGSubsampling = IJL_422;
jCprops.jquality = 100;

Is it right ?

[Vladimir_Dudnik]

Hi,

you can check with old IJL sample (please find it in attachment).

Regards,
Vladimir

[yasu]

Hi,

Thank you for your response.
I checked the sample. But, I think it is the same as my code.
I tried the following two patterns.

YCbCr422 ? JPEG

Result: It darkens compared with an original image.

YCbCr422 ? RGB24(DIB) ? JPEG

Result: It is almost the same as an original image.

Why do it become such a result
though and are thought becoming the same?

[Vladimir_Dudnik]

Hi,

could you please attach sample images, original and compressed, which became dark? I can't realize what is the problem. I tested some image with sample I attached here, this work and does not add dakness to image.

Regards,
Vladimir