Re: Problem with gray scale bitmap -- Envision Support Forum

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Date Posted: 15:18:18 10/14/05 Fri
Author: Roberto Pungartnik
Subject: Re: Problem with gray scale bitmap
In reply to: Michel 's message, "Re: Problem with gray scale bitmap" on 17:15:20 10/12/05 Wed

Hello Michel,

I have checked this and ImageFormat is ifColor256.

My question is, ImageLib can�t make difference from a 256 color image to a 256 gray level?

If it�s true, how can i open a gray level image to save as JPEG without need to make a FormatTransfor or a ConvertToGray?

I ask this becouse i will need some speed on this action, and on my tests this option take much more time that i have to spent on this task(convert from BMP to JPEG).

Thanks in Advance
Roberto Augusto

>
>Hi Roberto,
>
>Technically, there is no difference between a
>grayscale 256 and color 256 image. They both use a 256
>color palette, but with gray, all the R G and B values
>are the same.
>
>It depends how an image is manipulated before saving
>it as JPEG. Check the ImageFormat property of
>TDibGraphic before saving to see if it is ifColor256
>or ifGray256.
>
>Best regards,
>
>Michel
>
>>Hello,
>>
>>I�m trying to make a test software In Borland C++
>>Builder 5, that converts a 256 gray level bitmap to
>>JPEG, but when I try to convert, i receive the message
>>"JPEG must be gray scale or true color", but my image
>>is a 256 gray scale.
>>
>>In one of my tests i used the DemoC4.exe that i
>>generated from the samples.
>>
>>If I convert an image from 256 colors to gray scale,
>>and try to save as JPEG, it works fine, but if I save
>>the same image on gray scale(converted using the
>>DemoC4) and try to open(with DemoC4)and save as JPEG,
>>i got the same error.
>>
>>If i look at ImageScrollBox- Graphic- ImageFormat I
>>see that my 256 gray sacale image is opened as 256
>>colors, not as gray scale, this is a piece of my
>>code...
>>
>> TImageScrollBox *ImageScrollBox = new
>>TImageScrollBox( this );
>>
>> ImageScrollBox-> LoadFromFile( "ImgBase.bmp", 1 );
>>
>> ImageScrollBox-> SaveToFile( "ImgnJpg.jpg" );
>>
>> delete ImageScrollBox;
>>
>>Anyone have some ideia about this?
>>
>>Thanks in Advance
>>Roberto Augusto

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