Canon EOS-1D X Manual (en)

You can specify settings for processing images in DPP.
JPEG image quality
[Remove block noise and mosquito noise]
You can improve the quality of a JPEG image by reducing the noise 
particular to JPEG images. 
This setting is also effective when RAW images are converted to 
JPEG images and saved 
 and for JPEG images that to 
be saved with a different name. The higher the JPEG image’s 
compression rate, the better the effect. And when the compression 
rate is low, the effect of noise reduction may not be noticeable.
Image processing
Modified Picture Style settings
You can select whether the [Color tone], [Color saturation], [Contrast], 
[Unsharp mask] and [Sharpness] settings will be changed accordingly or 
retained, when you change the Picture Style.
If you checkmark the checkbox, the [Color tone], [Color saturation], 
[Contrast] and [Sharpness] settings will be changed to match the 
camera’s preset settings, when you change the Picture Style.
If you remove the check mark, the [Color tone], [Color saturation], 
[Contrast] and [Sharpness] settings will be retained, even if you 
change the Picture Style.