在 Embarcadero C++Builder 中反转位图

Question

The same problem happens in Borland C++Builder 6 and Embarcadero C++Builder 2010.

When I try to invert an image, the form freezes for about 5 seconds and nothing happens. When I click again, the image is inverted within a blink of an eye, and again, again...

To reproduce, create a form with a TImage and two TButton 's using this code:

//---------------------------------------------------------------------------
#include <vcl.h>
#include <jpeg.hpp>
#pragma hdrstop
#pragma package(smart_init)
#pragma resource "*.dfm"
#include "Unit1.h"
TForm1 *Form1;
Graphics::TBitmap *CurrentBitmap;
bool bLoaded = false;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) {
    CurrentBitmap = new Graphics::TBitmap;
}
//---------------------------------------------------------------------------
bool __fastcall Invert( TImage *img ) {
    if( bLoaded ) {
        double Scale, ScaleW, ScaleH;
        Graphics::TBitmap *bmp = new Graphics::TBitmap;
        bmp->Assign( CurrentBitmap );
        DWORD **pixel = new DWORD*[bmp->Height];
        for( long y=0; y<bmp->Height; y++ ) {
            pixel[y] = (DWORD*)(bmp->ScanLine[y]);
            for( long x=0; x<bmp->Width; x++ ) {
                if( pixel[y][x] == clBlack ) {
                    pixel[y][x] = clWhite;
                } else if( pixel[y][x] == clWhite ) {
                    pixel[y][x] = clBlack;
                }
            }

        }
        delete[] pixel;
        ScaleW = (double)bmp->Width / img->ClientWidth;
        ScaleH = (double)bmp->Height / img->ClientHeight;
        if( ScaleW > ScaleH ) {
            Scale = ScaleW;
        } else {
            Scale = ScaleH;
        }
        CurrentBitmap->Assign( bmp );
        img->Picture->Bitmap->Canvas->StretchDraw(Rect(0, 0, bmp->Width/Scale, bmp->Height/Scale), bmp );
        delete bmp;
        return true;
    } else {
        return false;
    }
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender) {
    TJPEGImage *jpg = new TJPEGImage();
    jpg->LoadFromFile( "V:\\CBuilder\\BCB10\\GerberTest\\Testdata\\GerberTest.dpi2400.mskcmp.jpg" );
    CurrentBitmap->Width = jpg->Width;
    CurrentBitmap->Height = jpg->Height;
    CurrentBitmap->Canvas->StretchDraw(Rect(0, 0, jpg->Width, jpg->Height), jpg );
    bLoaded = true;
    double Scale, ScaleW, ScaleH;
    ScaleW = (double)jpg->Width / Image1->ClientWidth;
    ScaleH = (double)jpg->Height / Image1->ClientHeight;
    if( ScaleW > ScaleH ) {
        Scale = ScaleW;
    } else {
        Scale = ScaleH;
    }
    Image1->Canvas->StretchDraw(Rect(0, 0, jpg->Width/Scale, jpg->Height/Scale), jpg );
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button2Click(TObject *Sender) {
    Invert( Image1 );
}

I cannot explain why the application freezes, or what the code is doing during the 5 second delay.

Answer 1

Like Remy Lebeau mentioned you should set the PixelFormat. I tried your solution which did not seems to invert images properly. Below you find a solution which should work properly.

#include <JPEG.hpp>

Byte __fastcall IntToByte(int AValue)
{
    if (AValue > 255)
        return 255;
    else if (AValue < 0)
        return 0;
    else
        return AValue;
}
// ---------------------------------------------------------------------------

void __fastcall InvertBitmap(Graphics::TBitmap *ABitmap)
{
    Byte *p0;
    int red, green, blue;
    for (int y = 0; y < ABitmap->Height; y++) {
        p0 = (Byte*) ABitmap->ScanLine[y];
        for (int x = 0; x < ABitmap->Width; x++) {
            red = p0[x * 3];
            green = p0[x * 3 + 1];
            blue = p0[x * 3 + 2];

            // invert
            red = 255 - red;
            green = 255 - green;
            blue = 255 - blue;

            p0[x * 3] = IntToByte(red);
            p0[x * 3 + 1] = IntToByte(green);
            p0[x * 3 + 2] = IntToByte(blue);
        }
    }
}
// ---------------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    Screen->Cursor = crHourGlass;
    TJPEGImage *jpeg = new TJPEGImage();
    Graphics::TBitmap *bitmap = new Graphics::TBitmap();
    try {
        jpeg->LoadFromFile("**YOUR-JPEG-FILE**");
        bitmap->SetSize(jpeg->Width, jpeg->Height);
        bitmap->Canvas->Draw(0, 0, jpeg);    
        bitmap->PixelFormat = pf24bit;
        InvertBitmap(bitmap);
        Image1->Picture->Bitmap->Assign(bitmap);
    }
    __finally {
        jpeg->Free();
        bitmap->Free();
    }
    Screen->Cursor = crDefault;
}
// ---------------------------------------------------------------------------