How to save a PNG or BMP transp with Freeimage (solved)

[ukoenig]

Hello,
is it possible, to save a Image ( BMP or PNG ) with transparent background ?

The sample shows a merged transparent-logo ( resized to 50 % ) on a transparent image exported to PNG.
I would like to save the main-image as transparent as well.
The exported file shows the transparent area in black.
It is possible, to do this with FREEIMAGE.



From FREEIMAGE documentation a sample :
( how to use this with Fivewin ? )

#include "FreeImage.h"
int main(int argc, char* argv[]) {
FIBITMAP *hDIB24bpp = FreeImage_Load(FIF_BMP, "test.bmp", 0);
if (hDIB24bpp) {
// color-quantize 24bpp (results in a 8bpp bitmap to set transparency)
FIBITMAP *hDIB8bpp = FreeImage_ColorQuantize(hDIB24bpp, FIQ_WUQUANT);
// get palette and find bright green
RGBQUAD *Palette = FreeImage_GetPalette(hDIB8bpp);
BYTE Transparency[256];
for (unsigned i = 0; i < 256; i++) {
Transparency[i] = 0xFF;
if (Palette[i].rgbGreen >= 0xFE &&
Palette[i].rgbBlue == 0x00 &&
Palette[i].rgbRed == 0x00) {
Transparency[i] = 0x00;
}
}
// set the tranparency table
FreeImage_SetTransparencyTable(hDIB8bpp, Transparency, 256);
// save 8bpp image as transparent PNG
FreeImage_Save(FIF_PNG, hDIB8bpp, "test.png", 0);
FreeImage_Unload(hDIB24bpp);
FreeImage_Unload(hDIB8bpp);
}
return 0;
}
FreeImage_SetTransparent

Best regards
Uwe

[ukoenig]

I found a solution, to add / merge a freestyle TRANSPARENT signature
to a image



My new Signature-painter :

Change color and pensize
erase parts of a signature
after erasing, use the last selected color



Best regards
Uwe