how to get the RGBA imge data ，i do this，but get nothing

[cyberdstar]

double x[] = { 0, 0.2, 0.4, 0.6, 0.8, 1.0 };
double y[] = { 0.3, 0.5, 0.4, 0.2, 0.6, 0.7 };
/* Draw something into the memory using GR / // 'RGBA'
// gr_openws(0, 0, 100);
char filename[64];
sprintf_s(filename, "!%dx%d@%p.mem", width, height, data);
// gr_setlinewidth(1);
gr_beginprint(filename);
gr_polyline(6, x, y);
gr_endprint();
std::vector vvc;
for (int j = 0; j < height; j++)
{
unsigned char pdata = &data[width * 4 * j];
for (uint64_t i = 0; i < (width * 4); i = i + 4)
{
vvc.push_back({pdata[i + 3],pdata[i + 0],pdata[i + 1] ,pdata[i + 2] });
}
}

[jheinen]

Could you pls send a complete code snippet, including all declarations?

[cyberdstar]

int width = 300;
int height = 300;
unsigned char* data = (unsigned char*)malloc(height * width * 4);       
memset(data, 0, height * width * 4);

double x[] = { 0, 0.2, 0.4, 0.6, 0.8, 1.0 };
double y[] = { 0.3, 0.5, 0.4, 0.2, 0.6, 0.7 };

/* Draw something into the memory using GR / // 'RGBA'
char filename[64];
sprintf_s(filename, "!%dx%d@%p.mem", width, height, data);
// gr_setlinewidth(1);
gr_beginprint(filename);
gr_polyline(6, x, y);
gr_endprint();
std::vector vvc;
for (int j = 0; j < height; j++)
{
unsigned char pdata = &data[width * 4 * j];
for (uint64_t i = 0; i < (width * 4); i = i + 4)
{
vvc.push_back({ pdata[i + 3],pdata[i + 0],pdata[i + 1] ,pdata[i + 2] });
}
}

winrt::array_view clr(vvc);
bitmap_image bi;
CanvasBitmap bp = CanvasBitmap::CreateFromColors(sender, clr, width, height);
Windows::Foundation::Numerics::float3x2 transform = Windows::Foundation::Numerics::make_float3x2_scale(sender.ActualWidth() / width, sender.ActualHeight() / height);
args.DrawingSession().Transform(transform);
args.DrawingSession().DrawImage(bp, 0, 0);
free(data);

[jheinen]

The following example works as expected. I used this include file, to save the byte array as a (transparent) PNG file.

/*
 cc -I /usr/local/gr/include tmem.c \
 -L/usr/local/gr/lib -lGR -Wl,-rpath,/usr/local/gr/lib
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "gr.h"
#include "svpng.inc"

int main(void)
{
    char filename[64];
    int i, width = 500, height = 500;
    unsigned char *data;
    double x[] = { 0, 0.2, 0.4, 0.6, 0.8, 1.0 };
    double y[] = { 0.3, 0.5, 0.4, 0.2, 0.6, 0.7 };

    data = (unsigned char *) malloc(height * width * 4);
    memset(data, 0, height * width * 4);

    sprintf(filename, "!%dx%d@%p.mem", width, height, data);
    gr_beginprint(filename);
    gr_polyline(6, x, y);
    gr_endprint();

    FILE *fp = fopen("rgba.png", "wb");
    svpng(fp, width, height, data, 1);
    fclose(fp);
}

[cyberdstar]

double x[] = { 0, 0.2, 0.4, 0.6, 0.8, 1.0 };
double y[] = { 0.3, 0.5, 0.4, 0.2, 0.6, 0.7 };

/* Draw something into the memory using GR / // 'RGBA'
char filename[64];
sprintf_s(filename, "!%dx%d@%p.mem", width, height, data);
gr_setlinewidth(3);
gr_beginprint(filename);
gr_polyline(6, x, y);
gr_endprint();
std::vector vvc;
for (int j = 0; j < height; j++)
{
unsigned char pdata = &data[width * 4 * j];
for (uint64_t i = 0; i < (width * 4); i = i + 4)
{
vvc.push_back({ pdata[i + 3],pdata[i + 0],pdata[i + 1] ,pdata[i + 2] });
}
}

FILE* fp = fopen("rgba.png", "wb");//严重性 代码 说明 项目 文件 行 禁止显示状态 详细信息
//错误 C4996 'fopen': This function or variable may be unsafe.Consider using fopen_s instead.To disable deprecation, use _CRT_SECURE_NO_WARNINGS.See online help for details.WaveFrontExperts E : \pwork\ky\WaveFrontExperts\MainWindow.xaml.cpp 157

svpng(fp, width, height, data, 1);
fclose(fp);

I do this，but still get a dark png not a curve imge

[cyberdstar]

think very much. i use msvc lib get noting,but with Windows (MinGW),get the correct result

[IngoMeyer441]

So you downloaded a pre-compiled version of GR on Windows?

It would be interesting for us to investigate, why the MSVC version behaves differently.