Just call SetOption(ImagingJpegQuality, 75)
between Img.LoadFromStream(mem_st) and Img.SaveToFile(str_file_path + 'jpg')

Try messing up with PixelBlendProc procedure in ImagingCanvases.pas. To preserve original alpha in dest image try if commenting out line
DestPix.A := SrcPix.A * FSrc.A + DestPix.A * FDst.A;
will do what you want to do.

Quote

Quotetry using SrcFactor: bfSrcAlpha and DestFactor: bfOneMinusSrcAlpha.

that will allways make all the alpha in the dest bitmap 255?...right?

Not always, but it changes dest alpha so it's not what you want.

Quoteso I guess Ill have to make my own blend mode

Something that uses the same factors as bfSrcAlpha+bfOneMinusSrcAlpha for
color channels only and bfZero+bfOne for alpha might work as you expect.

Quote

QuoteI'm going away now for a week or two so I can have a closer look after that.

Have Fun

It's a work trip, not so much fun :(

EDIT: Maybe some bool for canvas that says "don't touch alpha during blending"
might be useful, I guess preserving alphas is expected behavior here.

No, you have to use some additional library else for color profile handling.

Try asking in Lazarus forum (http://lazarus.freepascal.org/index.php?action=forum).
I'm using it only for Imaging demos - very rarely.

You could detect angles and lines using for example Hough transform (http://galfar.vevb.net/wp/2011/deskewing-scanned-documents/).

Has the example page moved somewhere?

Using StretchDrawAlpha doesn't do what you need?
To get regular alpha blending with DrawBlend
try using SrcFactor: bfSrcAlpha and DestFactor: bfOneMinusSrcAlpha.

I'm going away now for a week or two so I can have a closer look after that.

BTW: How are you using Imaging in Lua?

Checkout new raw IO functions in Imaging.pas (source in SVN):
ReadRawImageFromFile, ReadRawImageFromStream, etc.
You need to know the size and bit depth of the image of course.

It's stated here http://imaginglib.sourceforge.net/index.php?page=down
where the working code can be found but maybe it's not too obvious.

Updating the documentation, rebuilding demos, and testing the library on all supported platforms is quite long and not very exciting process. When I have some free time (not so much these days) to work on Imaging I'd rather implement some new features. Anyway, I'll have some free time over Christmas so I'll release new version then.

I'll add PSP loading for the next version (support probably similar like PSD now, flatten).
But I'm not sure if the format has not changed significantly since Corel took over JASC (I have only JASC PSP 9 for testing).

Do you really mean channels?
Or layers?

What graphic card and drivers are you using? There've been some driver related crashed before.
Could you post a full exception/error info that you get? Line number where the error happens
could help a lot in fixing this.
Or maybe post a source of your project?

Hi,
try the latest code from SVN please, that seems to open these JPEGs well.
There've been some JPEG related fixes since version 0.26.4.

Dekuji moc za donation ;D

You mean just raw data (pixel memory dumped to file) or Windows Bitmap format?

Jpeg quality is just for saving and it's used for quantization of DCT coefficients - basically it tells the Jpeg compressor how much information to throw away (lossy compression).
There's no original if the image is saved as Jpeg - each time you save it the image will lose
some information.