24 bits bitmap file to 256-color bitmap Conversion

{*************************************** *******************}
{}
{Image Conversion Processing Unit}
{Converting the 24 bits bitmap file to the 256-color bitmap file}
{*************************************** *******************}

// ================================================ ================================
// Program: Chen linmao
// Written on: 2002-06-28

// Contact Author: linmaochen@sohu.com
// ================================================ ================================

// ================================================ ================================
// Program function: converts an image in bitmap format to a JPEG image.
// Program conversion algorithm: use the default method in tbitmap and tjpeg for conversion
// First define a bitmap data source and import the image file to tbitmap;
// Define a JPEG data source and define its data source from tbitmap.
// ================================================ ==================================

Unit BMP jpg_unit;

Interface
Uses
Windows, messages, sysutils, classes, graphics, controls, forms, dialogs,
Stdctrls, buttons, JPEG;

// ================================================ ==================================
// Function: convert a bitmap file to a JPG file
// Function name: BMP tojpg
// Parameter description:
// BMP file: file in BMP format to be converted
// Jpgfile: the destination file to be converted to JPG format
// Compress: File compression ratio during conversion
// ================================================ ==================================
Function BMP tojpg (BMP file: string; jpgfile: string; compress: integer): Boolean;

Function jpgtobmp (jpgfile: string; BMP file: string; compress: integer): Boolean;

Implementation

// Convert BMP image to jpg image
Function BMP tojpg (BMP file: string; jpgfile: string; compress: integer): Boolean;
VaR
Bitmap: tbitmap;
Jpgimage: tsf-image;
Begin
Result: = false;
Try
Bitmap: = tbitmap. Create;
Jpgimage: = tsf-image. Create;
Bitmap. loadfromfile (BMP file );
Jpgimage. compressionquality: = compress;
Jpgimage. Performance: = jpbestquality;
Jpgimage. grayscale: = true;
Jpgimage. Smoothing: = true;
Jpgimage. Assign (Bitmap );
Jpgimage. Compress;
Jpgimage. savetofile (jpgfile );
Result: = true;
Except
End;
Bitmap. Free;
Jpgimage. Free;

End;

// Convert a jpg image to a 256-color BMP Image
Function jpgtobmp (jpgfile: string; BMP file: string; compress: integer): Boolean;
VaR
Bitmap: tbitmap;
Jpgimage: tsf-image;
Begin
Result: = false;
Try
Bitmap: = tbitmap. Create;
Jpgimage: = tsf-image. Create;
Jpgimage. loadfromfile (jpgfile );

Jpgimage. Performance: = jpbestquality;
Jpgimage. grayscale: = true;
Jpgimage. Smoothing: = true;

Bitmap. Assign (jpgimage );
Bitmap. dormant;

Bitmap. savetofile (BMP file );
Result: = true;
Except
End;
Bitmap. Free;
Jpgimage. Free;

 

End;

 

Begin

// Convert a 24-bit color image to a 256-color grayscale image

Jpgfilename: = _ apppath pai'temp.jpg ';
BMP filename: = _ apppath pai'temp.bmp ';
BMP tojpg (srcfilename, jpgfilename, 100 );
Jpgtobmp (jpgfilename, BMP filename, 100 );

// After the above two steps, the system automatically converts the 24 bits BMP to a 256-color bitmap and passes the test under Delphi5.0. Unfortunately, the color bitmap is converted to a grayscale image. Srcfilename: 24 bits BMP file.

End.