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Date Posted: 17:37:10 12/02/02 Mon
Author: Michel
Subject: Re: Size of resized image files
In reply to: Todd Cary 's message, "Re: Size of resized image files" on 11:59:26 11/30/02 Sat


Hi Todd,

Yes, email them to me at michel@intervalsoftware.com

I seem to recall about a very uncommon lossless jpg compression. This may be what PS is using.

Best regards,

Michel


>Would it be alright to send you a file containing the
>original, the "envision resized" and the "PhotoShop
>resized"?
>
>The resized are 750 pixels wide and the quality
>appears to be the same, except the PS file is 10 times
>bigger.
>
>Todd
>>
>>Hi Todd,
>>
>>Yes, Quality at 100 is the best you can get. I don't
>>know what Photoshop is doing. Is the image size
>>identical in Photoshop.
>>
>>Does the image saved with Envision appears visually as
>>the same quality?
>>
>>Best regards,
>>
>>Michel
>>
>>>First I convert the jpeg image to a bmp, then I use
>>>Melander's Stretch for the compression. Lastly, I
>set
>>>the Quality to 100 and convert the bmp back to a
>jpeg.
>>>
>>>Isn't this the maximum quality that I can use?
>>>
>>>Todd
>>>>
>>>>Hi Todd,
>>>>
>>>>First, BMP files usually don't have any compression,
>>>>so true color files are generally very large as Bmp.
>>>>BMP files may have RLE compression but it is not
>very
>>>>good and it not used very often.
>>>>
>>>>When saving as JPEG it is another story. JPEG uses a
>>>>lossy compression (you lose image quality, sometimes
>>>>not noticable). But if you continously open and save
>>a
>>>>JPG file you will see the degradation. This is why
>it
>>>>achieves great compression. Also, there are
>>difference
>>>>between jpg compression because jpg has a quality
>>>>factor which you can change while saving. Better
>>>>quality means less compression. This is probably the
>>>>difference between Envision and photoshop. See the
>>>>TJpegGraphic.SaveQuality property in the help file.
>>>>
>>>>Best regards,
>>>>
>>>>Michel
>>>>
>>>>
>>>>>If I use one of the filters to resize an jpeg image
>>>>>(750 X 450), I get approximately a 25 K file. The
>>>>>intermediate bmp file (if I save it for debugging
>>>>>reasons) is 18 MB.
>>>>>
>>>>>When I use PhotoShop to resize the same image, it
>is
>>>>>approximately 250 K. Why the difference?
>>>>>
>>>>>Todd

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