🚀 go-pugleaf

"Mario Sernicola" <mariosernicola@nospam.libero.it> wrote in message
news:40bcd795$1@newsgroups.borland.com...


>          Timage1->Canvas->Pen->Width = 1;
<snip>
> a message error appears:
>
> "Can only modify an image if it contains a bitmap"

The error is correct.  The Canvas property is only valid when the Picture
contains a TBitmap.

> How can I draw on TImage either if it contains a BMP or JPG???

You can't.  You would have to convert the JPG into a BMP first, then draw on
it, then convert it back into a JPG again.  The problem is that JPG is a
lossy format.  The more you alter it, the more image quality it loses.


Gambit

Ok, so I've to continue convert JPG into a BMP with an external software,
import the BMP in my TImage component, draw on it and finally import the JPG
in TImage.

I need to draw on TImage canvas in order to catch vertex pixel of a polygon
that describes a shape contained in TImage. When the vertex are know, I
don't need BMP anymore.

"Remy Lebeau (TeamB)" <gambit47.no.spam@no.spam.yahoo.com> ha scritto nel
messaggio news:40bd02cb@newsgroups.borland.com...
> > How can I draw on TImage either if it contains a BMP or JPG???
>
> You can't.  You would have to convert the JPG into a BMP first, then draw
on
> it, then convert it back into a JPG again.  The problem is that JPG is a
> lossy format.  The more you alter it, the more image quality it loses.
>
>
> Gambit
>
>

On Wed, 2 Jun 2004 09:48:56 +0200, "Mario Sernicola"
<mariosernicola@nospam.libero.it> wrote:

>Ok, so I've to continue convert JPG into a BMP with an external software,
No, you can make it on the fly. For example, with BCB6 it's pretty seamless.

>I need to draw on TImage canvas in order to catch vertex pixel of a polygon
>that describes a shape contained in TImage. When the vertex are know, I
>don't need BMP anymore.
Please, take the following snippet like a starting point for your further
experiments:

#include <memory>
#include <Jpeg.hpp>

using std::auto_ptr;

void ProcessTheImage( void )
{
    // crea una istanza di TJPEGImage e ci carica dentro una immagine 
    auto_ptr<TJPEGImage> const JPG( new TJPEGImage );
    JPG->LoadFromFile( "nome del file.jpg" );

    // crea una DIB e gli assegna il contenuto del JPEG precedentemente
    // creato
    auto_ptr<Graphics::TBitmap> const BMP( new Graphics::TBitmap );
    BMP->Assign( JPG.get() );

    // Aggiunge una ellisse, giusto per "sporcare" un pochino l'immagine
    // originale
    BMP->Canvas->Ellipse( 10, 10, 100, 200 );

    // assegna di nuovo l'immagine modificata al JPEG
    JPG->Assign( BMP.get() );

    // Salva su file, 
    JPG->SaveToFile( "nome del nuovo file.jpg" );

    // oppure... assegna il JPEG appena creato ad un componente TImage
    Image1->Picture->Bitmap->Assign( JPG.get() );
}

Ciao

Giuliano

Mario Sernicola wrote:

> Ok, so I've to continue convert JPG into a BMP with an external software,

No that has not been said.

> import the BMP in my TImage component, draw on it and finally import the JPG
> in TImage.

You can just make a bitmap yourself and draw the jpg on it.

Load the jpg in Image1 and place an extra TImage Image2 on your form:

  Graphics::TBitmap *bitmap = new Graphics::TBitmap;

  try
   {
    bitmap->Width  = Image1->Width;
    bitmap->Height = Image1->Height;

    bitmap->Canvas->Draw ( 0,0,Image1->Picture->Graphic);

    Image2->Picture->Bitmap->Assign ( bitmap );
     }
   catch ( Exception &exception )
      {
	//
      }

   delete bitmap;


> I need to draw on TImage canvas in order to catch vertex pixel of a polygon
> that describes a shape contained in TImage. When the vertex are know, I
> don't need BMP anymore.

You can use Image 2 for that. Or, even better, bitmap->Canvas.

Hans.

"Mario Sernicola" <mariosernicola@nospam.libero.it> wrote in message
news:40bd8664$1@newsgroups.borland.com...

> Ok, so I've to continue convert JPG into a BMP with an external software

Assuming you are using TJPEGImage, it already knows how to convert itself
to/from a TBitmap.  Just use the Assign() method, ie:

    Graphics::TBitmap *bmp = new Graphics::TBitmap;
    try
    {
        bmp->Assign(Image1->Picture->Graphic);
        // alter the bmp as needed...
        Image1->Picture->Graphic->Assign(bmp);
    }
    __finally {
        delete bmp;
    }

> import the BMP in my TImage component

No.  You operate on a separate TBitmap.  You do not put the bitmap into the
TImage while you are drawing on it.


Gambit

"Giuliano" <gcardinali@remove.adhoc.net> wrote in message
news:7s5rb05gt1theg28fcvkmrgd4jla7cvno1@4ax.com...

>     // oppure... assegna il JPEG appena creato ad un componente TImage
>     Image1->Picture->Bitmap->Assign( JPG.get() );

You can (and should) store the JPG into the TImage directly:

    Image1->Picture->Graphic = JPG.get();

TJPEGImage derives from TGraphic, and thus can be used with TPicture
directly.  Internally, the Graphic property will make a copy of the source
JPG.  Do not keep converting it to a bitmap.  The more conversions you do,
the more quality is lost from the image since JPG is a lossy format.


Gambit

On Wed, 2 Jun 2004 11:00:51 -0700, "Remy Lebeau \(TeamB\)"
<gambit47.no.spam@no.spam.yahoo.com> wrote:

>
>"Giuliano" <gcardinali@remove.adhoc.net> wrote in message
>news:7s5rb05gt1theg28fcvkmrgd4jla7cvno1@4ax.com...
>
>>     // oppure... assegna il JPEG appena creato ad un componente TImage
>>     Image1->Picture->Bitmap->Assign( JPG.get() );
>
>You can (and should) store the JPG into the TImage directly:
>
>    Image1->Picture->Graphic = JPG.get();
>
>TJPEGImage derives from TGraphic, and thus can be used with TPicture
>directly.  Internally, the Graphic property will make a copy of the source
>JPG.  Do not keep converting it to a bitmap.  The more conversions you do,
>the more quality is lost from the image since JPG is a lossy format.
>
>
>Gambit
>

Have you tried it?

"Giuliano" <gcardinali@remove.adhoc.net> wrote in message
news:e0rsb05dp8hb4tj7lmotgrpe1l18a9kt6v@4ax.com...

> ???

And your actual question is ... ?


Gambit

On Wed, 2 Jun 2004 17:25:55 -0700, "Remy Lebeau \(TeamB\)"
<gambit47.no.spam@no.spam.yahoo.com> wrote:

>
>"Giuliano" <gcardinali@remove.adhoc.net> wrote in message
>news:e0rsb05dp8hb4tj7lmotgrpe1l18a9kt6v@4ax.com...
>
>> ???
>
>And your actual question is ... ?
>
>
>Gambit
>

As far as I know, the JPGE algorithm is lossy when it encodes not when it
decodes.

Giuliano

On Thu, 3 Jun 2004 02:06:01 -0700, "Remy Lebeau \(TeamB\)"
<gambit47.no.spam@no.spam.yahoo.com> wrote:

>
>"Giuliano" <gcardinali@remove.adhoc.net> wrote in message
>news:kcktb098ube80ktpgcev2nmccevjlui7jc@4ax.com...
>
>> As far as I know, the JPGE algorithm is lossy
>> when it encodes not when it decodes.
>
>What do you think is happening when you assign a BMP to a JPG?  It encodes
>it.  You assign a bitmap to a JPG, you lose a little.  Then you decode the
>reduced JPG to a bitmap and then encode it back to a JPG, thus losing a
>little again.  See the pattern?
>
>
>Gambit
>

What do you think is happening when you assign a JPG to a BMP? 

    Image1->Picture->Bitmap->Assign( JPG.get() );

It converts the JPG in a DIB (or DDB) and it's loseless because the lossy is
in the encoding operation, so doing 

    Image1->Picture->Bitmap->Assign( JPG.get() );

or dooing

    Image1->Picture->Bitmap->Assign( JPG.get() );

or

    Image1->Picture->Graphic = JPG.get();

is the same thing.

See the picture?

Giuliano

On Thu, 3 Jun 2004 02:06:01 -0700, "Remy Lebeau \(TeamB\)"
<gambit47.no.spam@no.spam.yahoo.com> wrote:

>What do you think is happening when you assign a BMP to a JPG?  It encodes
>it.  You assign a bitmap to a JPG, you lose a little.  Then you decode the
>reduced JPG to a bitmap and then encode it back to a JPG, thus losing a
>little again.  See the pattern?

...moreover because, AFAIK, you can't modify the JPEG directly in TImage, yuo
have to pass for a DIB then converting it into a JPEG again if you want a JPEG
back. So this operation is lossy.
Again, the GDI is not capable to display a JPEG directly becuase it should
need to convert the JPEG into a DIB (or DDB) before to display it. So, in the
VCL layer, the conversion from JPG to DIB od DDB has to happen, wich is
loseless beacuse it's a decoding.

"Giuliano" <gcardinali@remove_adhoc.net> wrote in message
news:40beec16.149288578@newsgroups.borland.com...

> It converts the JPG in a DIB (or DDB) and it's loseless
> because the lossy is in the encoding operation

Which is what happens when you assign the bitmap *back* to the JPG after
modifying it:

    JPG->Assign(TheBitmap);


Gambit

"Giuliano" <gcardinali@remove_adhoc.net> wrote in message
news:40bfecf8.149514656@newsgroups.borland.com...

> ...moreover because, AFAIK, you can't modify the JPEG directly
> in TImage, yuo have to pass for a DIB then converting it into a
> JPEG again if you want a JPEG back. So this operation is lossy.

Which is what I said 2 days ago in my original reply.


Gambit

On Thu, 3 Jun 2004 10:10:55 -0700, "Remy Lebeau \(TeamB\)"
<gambit47.no.spam@no.spam.yahoo.com> wrote:

>
>"Giuliano" <gcardinali@remove_adhoc.net> wrote in message
>news:40beec16.149288578@newsgroups.borland.com...
>
>> It converts the JPG in a DIB (or DDB) and it's loseless
>> because the lossy is in the encoding operation
>
>Which is what happens when you assign the bitmap *back* to the JPG after
>modifying it:
>
>    JPG->Assign(TheBitmap);
>
>
>Gambit
>

Really?     
What if I would like to create a modified JPEG from another JPEG?  
This how my original snipped was conceived.    
Has this so much annoyed you? 
For the original poster this should be a starting point. 

On Thu, 3 Jun 2004 10:12:22 -0700, "Remy Lebeau \(TeamB\)"
<gambit47.no.spam@no.spam.yahoo.com> wrote:

>
>"Giuliano" <gcardinali@remove_adhoc.net> wrote in message
>news:40bfecf8.149514656@newsgroups.borland.com...
>
>> ...moreover because, AFAIK, you can't modify the JPEG directly
>> in TImage, yuo have to pass for a DIB then converting it into a
>> JPEG again if you want a JPEG back. So this operation is lossy.
>
>Which is what I said 2 days ago in my original reply.
>
>
>Gambit
>

And what it has added your useless comment to my reply?

"Giuliano" <gcardinali@remove.adhoc.net> wrote in message
news:nucvb0lqi70qn3vakejidh82d0htl0cdft@4ax.com...

> Really?
> What if I would like to create a modified JPEG from another JPEG?

Without seeing TJPEGImage's actual source code (which Borland does not
distribute) I would image that it is able to do a direct copy without any
lose of data.

> This how my original snipped was conceived.

Your original code was assigning the JPG to a BMP and then assigning the BMP
back to the JPG again.


Gambit