Hello, I had this working before but for some reason I now get fully
transparent PNG files, i.e. with no images in them, for all _except_ the first
PNG file I generate. E.g. the program below makes a good 1.png, but
2.png is just transparent (pnginfo says all the colours used in it are
transparent). I know this because if I use "optimise", it says e.g. "2
colours, 2 transparent". Everything works fine when not using the 8bit
option.
Best regards,
Torquil Sørensen
********* "pnginfo" has the following to say about 1.png and 2.png: ***
1.png...
Image Width: 800 Image Length: 600
Bitdepth (Bits/Sample): 8
Channels (Samples/Pixel): 1
Pixel depth (Pixel Depth): 8
Colour Type (Photometric Interpretation): PALETTED COLOUR (256 colours, 0
transparent)
Image filter: Single row per byte filter
Interlacing: No interlacing
Compression Scheme: Deflate method 8, 32k window
Resolution: 0, 0 (unit unknown)
FillOrder: msb-to-lsb
Byte Order: Network (Big Endian)
Number of text strings: 0 of 0
Offsets: 0, 0
2.png...
Image Width: 800 Image Length: 600
Bitdepth (Bits/Sample): 8
Channels (Samples/Pixel): 1
Pixel depth (Pixel Depth): 8
Colour Type (Photometric Interpretation): PALETTED COLOUR with alpha (256
colours, 144 transparent)
Image filter: Single row per byte filter
Interlacing: No interlacing
Compression Scheme: Deflate method 8, 32k window
Resolution: 0, 0 (unit unknown)
FillOrder: msb-to-lsb
Byte Order: Network (Big Endian)
Number of text strings: 0 of 0
Offsets: 0, 0
****************** Here is the program: ********************
#include <plplot/plplot.h>
using namespace std;
int main()
{
plsdev("xwin"); // Screen plot
plinit();
plenv(0, 1, 0, 1, 1, -2);
plsstrm(1); plsdev("png"); // PNG plot
plsfam(1,0,1); plsfnam("%n.png");
plsetopt("drvopt", "8bit");
plinit();
plenv(0, 1, 0, 1, 1, -2);
double x[] = {0.0, 1.0}, y[] = {0.0, 0.5};
plsstrm(0);
plbop(); plline(2, x, y); pleop();
plsstrm(1); plcpstrm(0, 1);
plbop(); plreplot(); pleop();
plsstrm(0);
plbop(); plline(2, y, x); pleop();
plsstrm(1); plcpstrm(0, 1);
plbop(); plreplot(); pleop();
plend();
return(0);
}
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