DIGSSTV - Saving Images

How DIGSSTV images are saved will make a difference in their file size. The increase in file size may be significant, but the image content may only change slightly.



These pictures will illustrate:


lir.png

[lir.png]


This image was created from the Kodak Photo CD Sampler.
Then resampled and cropped using Paint Shop Pro.
Size = 125,056 Bytes - PNG file

sent297.jpg

[sent297.jpg]


The PNG image was copied from Paint Shop Pro and then pasted into DIGSSTV.
DIGSSTV converts the image to JPEG prior to sending.
High Quality was selected - transmission time = 297 seconds.
Size = 28,027 Bytes - JPEG file

temp.jpg

[temp.jpg]


This is the image file that the DIGSSTV saved in the DIGSSTV folder.
It is always given the name "temp.jpg".
This file is exactly like the JPEG file the sending station sent.
Size = 28,027 Bytes - JPEG file

DIGPIC030119125845.jpg

[digpic030119125845.jpg]


This image file was created by the beta version 15JAN03 of DIGSSTV
using the auto-save feature.
The name, "DIGPIC030119125845.jpg" is selected automatically by the program.
Size = 48,602 Bytes - JPEG file

yzsaveas.jpg

[yzsaveas.jpg]


This image file was created by DIGSSTV with the "Save As" feature.
JPEG was selected as the file type.
Size = 48,602 Bytes - JPEG file

yzsaveas.png

[yzsaveas.png]


This image file was created by DIGSSTV with the "Save As" feature.
PNG was selected as the file type.
Size = 114,743 Bytes - PNG file

Analysis

With the use of Paint Shop Pro using the Arithmetic Difference feature, it was found that each time an original image was loaded in High Quality, the converted image was changed in picture content. Received image was always identical to the transmitted image. How the received image is saved may change the image.


Conclusions

Replays of images going through the RX and TX screens will always have some change in picture content. Using "Save As" and saving in JPEG will further the change in picture content. Even the auto-save JPEG image will suffer this change. Using "Save As" and saving in PNG format will NOT change the image content from the received "temp.jpg" ! The only way DIGSSTV may send and replay without any changes at all is to use the "Load ANY file" feature.


  • More DIGSSTV Pictures

    More DIGSSTV Links: CQ SSTV
    73 Dave KB4YZ