StretchBlt 打印时失败

发布于 2024-07-12 11:12:18 字数 1253 浏览 2 评论 0原文

我有一个图表（位图格式），我正在尝试使用 StretchBlt 将其渲染到打印机。当绘制到屏幕上时，StretchBlt 工作正常。当绘制到 CutePDF 打印机时，它返回 0，将最后一个错误设置为 ERROR_INVALID_HANDLE，并且仍然可以工作。当绘制到 PDF995 打印机或物理 HP 打印机时，它返回 0，将最后一个错误设置为 ERROR_INVALID_HANDLE，并且无法绘制任何内容。

什么会导致 StretchBlt 在某些设备上失败？我已通过调用 GetDeviceCaps 验证源位图是 DIB 并且目标支持 StretchBlt。

这是我的代码，以防相关：（它是用 C++Builder 编写的，因此它使用 Delphi 的 VCL；TCanvas 包装 HDC，TBitmap 包装 HBITMAP。VCL 提供自己的 StretchDraw 函数，它可以不支持半色调；我遇到了同样的问题。）

void PrettyStretchDraw(TCanvas *dest, const TRect& rect, TGraphic *source)
{
  if (dynamic_cast<Graphics::TBitmap*>(source) && !source->Transparent) {
    POINT pt;
    GetBrushOrgEx(dest->Handle, &pt);
    SetStretchBltMode(dest->Handle, HALFTONE);
    SetBrushOrgEx(dest->Handle, pt.x, pt.y, NULL);
    StretchBlt(
      dest->Handle,
      rect.Left,
      rect.Top,
      rect.Width(),
      rect.Height(),
      dynamic_cast<Graphics::TBitmap*>(source)->Canvas->Handle,
      0,
      0,
      source->Width,
      source->Height,
      SRCCOPY);
  } else {
    DrawItSomeOtherWay(dest, rect, source);
  }
}

原文

I have a chart (in bitmap format) that I'm trying to render to a printer using StretchBlt. When drawing to the screen, StretchBlt works fine. When drawing to a CutePDF printer, it returns 0, sets the last error to ERROR_INVALID_HANDLE, and works anyway. When drawing to a PDF995 printer or a physical HP printer, it returns 0, sets the last error to ERROR_INVALID_HANDLE, and fails to draw anything.

What would cause StretchBlt to fail for certain devices? I've verified that the source bitmap is a DIB and that the destination supports StretchBlt by calling GetDeviceCaps.

Here's my code, in case it's relevant: (It's written in C++Builder, so it uses Delphi's VCL; TCanvas wraps an HDC, and TBitmap wraps an HBITMAP. VCL provides its own StretchDraw function which does not support HALFTONE; I'm getting the same problems with it.)

void PrettyStretchDraw(TCanvas *dest, const TRect& rect, TGraphic *source)
{
  if (dynamic_cast<Graphics::TBitmap*>(source) && !source->Transparent) {
    POINT pt;
    GetBrushOrgEx(dest->Handle, &pt);
    SetStretchBltMode(dest->Handle, HALFTONE);
    SetBrushOrgEx(dest->Handle, pt.x, pt.y, NULL);
    StretchBlt(
      dest->Handle,
      rect.Left,
      rect.Top,
      rect.Width(),
      rect.Height(),
      dynamic_cast<Graphics::TBitmap*>(source)->Canvas->Handle,
      0,
      0,
      source->Width,
      source->Height,
      SRCCOPY);
  } else {
    DrawItSomeOtherWay(dest, rect, source);
  }
}

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