basically it'sa a piece of piss to convert from bitmap to JPEG:
Here's a teeny snippet that does it for me, loading a JPEG into a
TImage. The same principle will work for other JPEG -> BMP ops:
VAR
TempJPEG : TJPEGImage;
Begin
...
TempJPEG := TJPEGImage.Create;
TempJPEG.LoadFromFile(Filename);
Image.Picture.Bitmap.Assign(TempJPEG);
TempJPEG.Free;
...
but...
[re the complexities]
*************************************************************************************
Code to load an image file such that
if the image is in bitmap format then
convert it to a JPEG (if it's already
a JPEG don't convert it, obviously).
Furthermore, we can change both the
quality and the size of the image as
required. The third parameter to the
CopyToJpeg function determines the
image quality, while all images bigger
than 216 by 185 are scaled to 216 by
185.
Note that the actual conversion from
.bmp to .jpg format is actually just
a single line of code.
Richard Ebbs and
Kristian Whittick
Jan 2000
unit BMP2JPEG;
interface
uses
Graphics, JPEG;
type
TWhatever = class(TObject)
function CopyToJpeg(const Source, Dest: String; Quality: Integer): Boolean;
private
public
end;
example call:
CopyToJpeg(EstateData.DataDir + FsourceName, WorkDir + FDestName, 0);
function CopyToJpeg(const Source, Dest: String; Quality: Integer): Boolean;
var
FileLoadImg : TImage;
ScaledImage : TImage;
JPEGimg : TJPEGImage;
scale : single;
Myrect : Trect;
NewWGap : integer;
NewHGap : integer;
begin
FileLoadImg := TImage.Create(nil);
ScaledImage := TImage.Create(nil);
JPEGimg := TJPEGImage.Create;
case quality of
0:
begin
JPEGimg.CompressionQuality := 100;
ScaledImage.AutoSize := False;
ScaledImage.Width := 216;
ScaledImage.Height := 185;
end;
1:
begin
JPEGimg.CompressionQuality := 50;
ScaledImage.AutoSize := False;
ScaledImage.Width := 432;
ScaledImage.Height := 305;
end;
else
JPEGimg.CompressionQuality := 100;
ScaledImage.AutoSize := true;
end;
try
JPEGimg.ProgressiveEncoding := True;
FileLoadImg.Picture.LoadFromFile(Source);
if (FileLoadImg.Width = 0) or (FileLoadImg.Height = 0) then
begin
result := False;
exit;
end;
case quality of
0, 1:
begin
if (ScaledImage.Width / FileLoadImg.Width) > (ScaledImage.Height / FileLoadImg.Height) then
scale := (ScaledImage.Height / FileLoadImg.Height)
else
scale := (ScaledImage.Width / FileLoadImg.Width);
Myrect.Left := 0; // Empty Image
Myrect.Top := 0;
Myrect.Right := ScaledImage.Width;
Myrect.Bottom := ScaledImage.Height;
ScaledImage.Canvas.Brush.Color := clWhite;
ScaledImage.Canvas.FillRect(MyRect);
NewWGap := Round((ScaledImage.Width - (FileLoadImg.Width * Scale)) / 2);
NewHGap := Round((ScaledImage.Height - (FileLoadImg.Height * Scale)) / 2);
Myrect.Left := NewWGap;
Myrect.Top := NewHGap;
Myrect.Right := ScaledImage.Width - NewWGap;
Myrect.Bottom := ScaledImage.height - NewHGap;
ScaledImage.Canvas.StretchDraw(Myrect, FileLoadImg.Picture.Graphic);
JPEGimg.Assign(ScaledImage.Picture.Bitmap);
end;
else
JPEGimg.Assign(FileLoadImg.Picture.Bitmap);
end;
JPEGimg.JPEGNeeded;
JPEGimg.SaveToFile(Dest);
result := True;
except
result := False;
end;
FileLoadImg.Free;
ScaledImage.Free;
JPEGimg.Free;
end;
*************************************************************************************
Hi Nick,
> Does anyone know how can I convert a BitMap (Bmp) to JPEG image?
Delphi comes with a nice new component called TJPEGImage, which can be
found in the JPEG unit. The TJPEGImage component is derived from
TGraphic, and hence probably Assign-compatible with a TBitmap (also
derived form TGraphic). The following code shows that this trick indeed
works: we can "Assign" an instance of a TBitmap to an instance of a
TJPEGImage. And using that information, we can write a simple CONSOLE
application to convert a given .BMP file to a .JPG file as follows:
{$APPTYPE CONSOLE}
uses
Classes, Graphics, JPEG, SysUtils;
var
Bitmap: TBitmap;
Stream: TFileStream;
begin
writeln('BMP2JPG 1.0 by Bob Swart (aka Dr.Bob - www.drbob42.com)');
if ParamCount = 0 then
begin
writeln('Usage: BMP2JPG file.bmp [%%]');
writeln;
writeln('Where "file.bmp" is the BMP file to convert to JPG,');
writeln('and %% is the compression quality (100% by default)')
end
else
begin
Bitmap := TBitmap.Create;
try
Bitmap.LoadFromFile(ParamStr(1));
with TJPEGImage.Create do
try
Assign(Bitmap);
if ParamCount > 1 then
try
CompressionQuality := StrToInt(ParamStr(2))
except
CompressionQuality := 100
end;
Stream :=
TFileStream.Create(ChangeFileExt(ParamStr(1),'.JPG'),fmCreate);
try
SaveToStream(Stream)
finally
Stream.Free
end
finally
Free
end
finally
Bitmap.Free
end
end
end.
Note that the TBitmap has a LoadFromFile method that we can use to load
a file, say DRBOB.BMP, into the bitmap, while we must use the
SaveToStream method from the TJPEGImage to save the JPEG image to a file
stream again (for some reason the latter doesn't appear to have a
SaveToFile).
Note also that the second command-line argument is used as the
compression quality percentage, which is 100% by default (for a small
raster with no loss of information). As an example, I converted the
44,280 bytes HANDSHAK.BMP file (from the IMAGES\SPLASH\256COLOR
directory) to seven JPEG files with compression qualities 100%, 90%,
89%, 80%, 70%, 60% and 50%. With 50% the images was no longer good in
quality. In practice, I use anything above 70% to get a good filesize
reduction but with a good picture left as well. Experiment with your own
BMP files to get a feeling...
Groetjes,
Bob Swart (aka Dr.Bob - www.drbob42.com)
--
drs. Robert E. (Bob) Swart, @-Consultant, Delphi Trainer & Author
Delphi OplossingsCentrum (DOC) & UK-BUG Borland User Group member
***************************************************************************************
ENCRYPTING IMAGES
I use the free ware THKStreams. I use this to compress my images and
embed them right into my EXE. As well as compressing, THKStream gives
an encryption option.
http://kakoulidis.homepage.com
Here is how I do this in my apps.
1. I take an image.
2. I compress the image to a HKStream compressed file. I can put more
than one image in a file. Matter of fact, I put all 15 of my images in the same
file with a tag for each image.
3. I wrote a simple tool that reads the file and builds a large CONST Byte Array
in a Delphi Unit file.
4. I include the Unit in my program.
5. I stream the Byte array into THKStream.
6. I use HKStream to uncompress my images.
7. My images are available in memory for the life of the app with everything all
in one EXE. Makes for easy install/deliver.