更新3-4-15：11IS 正如David修改PInvoke所建议的那样，这次我得到了不同的错误＆＃34; mscorlib.dll中发生了System.ExecutionEngineException类型的未处理异常＆＃34;
[DllImport("C:\\Program Files\\DJVULIBRE\\LIBDJVULIBRE.dll", CharSet=CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
private unsafe static extern int ddjvu_page_render(IntPtr page, ddjvu_render_mode_t mode, ref ddjvu_rect_t pagerect,
ref ddjvu_rect_t renderrect,
IntPtr pixelformat,
uint rowsize,
[Out][MarshalAs(UnmanagedType.LPArray)]byte[] imagebuffer);
感谢大卫宝贵的时间，我认为已接近修复。
记录
我知道这个问题有很多问题，但没有一个问题有助于解决我目前面临的问题。
以下是C语言中的API函数
DDJVUAPI int
ddjvu_page_render(ddjvu_page_t *page,
const ddjvu_render_mode_t mode,
const ddjvu_rect_t *pagerect,
const ddjvu_rect_t *renderrect,
const ddjvu_format_t *pixelformat,
unsigned long rowsize,
char *imagebuffer );
下面是在.NET代码中添加的C函数的PInvoke签名
[DllImport("C:\\Program Files\\DJVULIBRE\\LIBDJVULIBRE.dll", CharSet=CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
private unsafe static extern int ddjvu_page_render(IntPtr page, ddjvu_render_mode_t mode, IntPtr pagerect,
IntPtr renderrect,
IntPtr pixelformat,
ulong rowsize,
[Out][MarshalAs(UnmanagedType.LPArray)]byte[] imagebuffer);
以下是我在c＃代码中调用此函数的方法
byte* buffer = (byte *)Memory.Alloc(nSize);
try
{
IntPtr ptr1 = (IntPtr)Memory.Alloc(Marshal.SizeOf(prect));
Marshal.StructureToPtr(prect, ptr1, false);
IntPtr ptr2 = (IntPtr)Memory.Alloc(Marshal.SizeOf(rrect));
Marshal.StructureToPtr(rrect, ptr2, false);
byte[] array = new byte[nSize];
fixed (byte* p = array) Memory.Copy(buffer, p, nSize);
ddjvu_page_render(page, ddjvu_render_mode_t.DDJVU_RENDER_MASKONLY, ptr1, ptr2, fmt, (ulong)stride, array);
}
finally
{
Memory.Free(buffer);
}
在上面的代码中调用ddjvu_page_render正在抛出＆＃34;尝试读取或写入受保护的内存。这通常表明其他内存已损坏。＆＃34; 在这篇文章之前，我必须尝试在各种博客中找到的所有选项。 感谢任何帮助，几乎是一天我无能为力，你的及时帮助可以挽救我的工作
更新3-4-15：7：44IS 此代码使用DJVULibre
更新3-4-15：8：35IS
这是我在Form Load
中的代码 ctx = ddjvu_context_create(System.AppDomain.CurrentDomain.FriendlyName);
if (ctx != null)
{
string djFile = "C:\\Users\\rammohan.chavakula\\Documents\\eiasample.djvu";
doc = ddjvu_document_create_by_filename(ctx, djFile, 100);
if (doc != null)
{
while (ddjvu_job_status(ddjvu_document_job(doc)) >= ddjvu_status_t.DDJVU_JOB_OK)
SpinDdjvuMessageLoop(ctx, true);
int pageCount = ddjvu_document_get_pagenum(doc);
mediaboxes = new Rectangle[pageCount];
for (int i = 0; i < pageCount; i++)
{
ddjvu_status_t status;
ddjvu_pageinfo_t info = new ddjvu_pageinfo_t();
while ((status = ddjvu_document_get_pageinfo_imp(doc, i, ref info, (uint)System.Runtime.InteropServices.Marshal.SizeOf(info))) < ddjvu_status_t.DDJVU_JOB_OK)
SpinDdjvuMessageLoop(ctx, true);
if (status != ddjvu_status_t.DDJVU_JOB_OK)
continue;
mediaboxes[i] = new Rectangle(0, 0, info.width / info.dpi,
info.height / info.dpi);
}
}
ddjvu_context_release(ctx);
}
在OnPaint功能中，我有以下代码
if (doc == null)
{
base.OnPaint(e);
return;
}
Rectangle pageRc = PageMediabox(1);
Rectangle screen = Transform(pageRc, 1, zoom, rotation, false);
Rectangle full = Transform(PageMediabox(1), 1, zoom, rotation, false);
full.Intersect(screen);
IntPtr page = ddjvu_page_create_by_pageno(doc, 1);
if (page == null )
{
base.OnPaint(e);
return;
}
int rotation4 = (((-rotation / 90) % 4) + 4) % 4;
ddjvu_page_set_rotation(page, (ddjvu_page_rotation_t)rotation4);
while (ddjvu_job_status(ddjvu_page_job(page)) >= ddjvu_status_t.DDJVU_JOB_OK)
SpinDdjvuMessageLoop(ctx, true);
if (ddjvu_job_status(ddjvu_page_job(page)) >= ddjvu_status_t.DDJVU_JOB_FAILED)
{
base.OnPaint(e);
return;
}
IntPtr fmt = ddjvu_format_create(ddjvu_format_style_t.DDJVU_FORMAT_BGR24, 0, (UIntPtr)null);
ddjvu_format_set_row_order(fmt, /* top_to_bottom */1);
ddjvu_rect_t prect = new ddjvu_rect_t(full.X, full.Y, (uint)full.Width, (uint)full.Height);
ddjvu_rect_t rrect = new ddjvu_rect_t(screen.X, 2 * full.Y + screen.Y + full.Height - screen.Height, (uint)screen.Width, (uint)screen.Height);
int stride = ((screen.Width * 3 + 3) / 4) * 4;
//byte tmp;
////ScopedMem<char> bmpData(SAZA(char, stride * (screen.dy + 5)));
//for (int y = 0; y < rrect.h; y++) {
// int step_y = y * SCREEN_WIDTH;
// for (int x=0; x < rrect.w; x++) {
// tmp = (byte)((imagebuf[x + step_y] >> 5) << 5);
// }
//}
int rowsize = mediaboxes[0].Width * 3;
int nSize = rowsize * (mediaboxes[0].Height) * 10;
unsafe
{
byte* buffer = (byte *)Memory.Alloc(nSize);
try
{
IntPtr ptr1 = (IntPtr)Memory.Alloc(Marshal.SizeOf(prect));
Marshal.StructureToPtr(prect, ptr1, false);
IntPtr ptr2 = (IntPtr)Memory.Alloc(Marshal.SizeOf(rrect));
Marshal.StructureToPtr(rrect, ptr2, false);
byte[] array = new byte[nSize];
fixed (byte* p = array) Memory.Copy(buffer, p, nSize);
ddjvu_page_render(page, ddjvu_render_mode_t.DDJVU_RENDER_MASKONLY, ptr1, ptr2, fmt, (ulong)stride, array);
}
finally
{
Memory.Free(buffer);
}
ddjvu_page_render应返回要在给定矩形区域中呈现的页面的任意数据。之后，我应该能够从任意数据创建图像＆amp;显示在屏幕上
答案 0 :(得分：0)
以下是我将如何编写p / invoke：
[DllImport(dllname, CharSet=CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
private static extern int ddjvu_page_render(
[In] IntPtr page,
[In] ddjvu_render_mode_t mode,
[In] ref ddjvu_rect_t pagerect,
[In] ref ddjvu_rect_t renderrect,
[In] ref ddjvu_format_t pixelformat,
[In] uint rowsize,
[Out] byte[] imagebuffer
);
请注意，我已停止使用unsafe，并让编组人员自动处理结构。
这里有一些我无法验证的假设：
void*句柄类型，我猜是。ddjvu_render_mode_t是您已正确翻译的枚举。ref参数是结构，通过引用传递。我无法检查您是否正确翻译了它们。调用此函数将是这样的：
byte[] imagebuffer = new byte[nSize];
int retval = ddjvu_page_render(
page,
ddjvu_render_mode_t.DDJVU_RENDER_MASKONLY,
ref prect,
ref rrect,
ref fmt,
(uint)stride,
imagebuffer
);
if (retval != ??)
// handle error
这是一个非常广泛的答案。我希望它能指出你正确的方向。我不认为你的所有问题都会被解决。