标准固定
1 寸=3.3333333 厘米
1 英寸=2.54 厘米
求计算机显示器PPI?
比如对角线14英寸，不是寸，即2.54*14=35.56cm
按16:9算出宽和高 高(9x)2+宽（16x）2=对角线35.56cm2 算出宽*高：30.99*17.43cm 即30.99/2.54英寸
像素为1920*1080 PPI=1920*2.54/30.99= 约157PPI(pixel per inch)
求一张图片在某分辨率下的实际尺寸？
比如600PPI(pixel per inch 显示器)或DPI(dots per inch 打印机) ，像素为1920*1080，算宽*高各为多少英寸或厘米？
像素为1920*1080，打印机为600dpi
宽=1920/600 英寸=1920/600*2.54 厘米=8.128 厘米
高=1080/600 英寸=1080/600*2.54 厘米=4.572 厘米
现在改为打印机300dpi，要求实际物理尺寸不变。
宽=width/300 英寸=width/300*2.54 厘米=8.128 厘米
高=height/300 英寸=height/300*2.54 厘米=4.572 厘米
必须缩放图片像素为960*540
所以，不同点数的打印机要按实际物理尺寸打印图片，那必须缩放图片,即改变像素。实际尺寸以打印机为600dpi为标准：currnet_x_pix=old_x_pix/600*currnet_dpi
C#按物理尺寸打印图片 e.Graphics.DrawImage(image,0,0)； //按物理尺寸打印标签，600点改为300点的打印机_小黄人软件的博客-CSDN博客
MFC按实际物理尺寸打印图片
方法1.获得打印机点数，按点数转换图片像素
#include "pch.h"
#include "../pch.h"
#include "../utility/utility.h"
#include <atlbase.h>
using namespace Gdiplus;
int GetEncoderClsid(const WCHAR* format, CLSID* pClsid)
{
UINT num = 0; // number of image encoders
UINT size = 0; // size of the image encoder array in bytes
ImageCodecInfo* pImageCodecInfo = NULL;
GetImageEncodersSize(&num, &size);
if (size == 0)
return -1; // Failure
pImageCodecInfo = (ImageCodecInfo*)(malloc(size));
if (pImageCodecInfo == NULL)
return -1; // Failure
GetImageEncoders(num, size, pImageCodecInfo);
for (UINT j = 0; j < num; ++j)
{
if (wcscmp(pImageCodecInfo[j].MimeType, format) == 0)
{
*pClsid = pImageCodecInfo[j].Clsid;
free(pImageCodecInfo);
return j; // Success
}
}
free(pImageCodecInfo);
return -1; // Failure
}
BOOL getBMPInfo(LPCTSTR fileName)
{
// Initialize GDI+.
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
USES_CONVERSION;
Gdiplus::Bitmap* pBitmap = new Gdiplus::Bitmap(T2W(fileName));
if (pBitmap == NULL || pBitmap->GetLastStatus() != Gdiplus::Ok) { logger.ERROR_F(__FUNCTION__+to_string(__LINE__)+"出错:" + to_string(pBitmap->GetLastStatus())); delete pBitmap; return FALSE; }
logger.INFO_F("水平*垂直分辨率:" +to_string(pBitmap->GetHorizontalResolution()) + "*" + to_string(pBitmap->GetVerticalResolution()));
logger.INFO_F("width*height像素:" + to_string(pBitmap->GetWidth())+"*"+ to_string(pBitmap->GetHeight()));
logger.INFO_F("600dpi时width*height厘米:" + to_string((float)(pBitmap->GetWidth())*2.54 /600) + "*" + to_string((float)(pBitmap->GetHeight())*2.54 /600));
//if (abs(pBitmap->GetHorizontalResolution() - dpi)>0.5 || abs(pBitmap->GetVerticalResolution() - dpi)> 0.5)
//{
// logger.ERROR_F("水平分辨率" + to_string(pBitmap->GetHorizontalResolution()) + "或垂直分辨率" + to_string(pBitmap->GetVerticalResolution()) + " 错误,应该为" + to_string(dpi));
// delete pBitmap;
// return FALSE;
//}
delete pBitmap;
return TRUE;
}
BOOL setBMPResolution(LPCTSTR fileName, float dpi)
{
LPCTSTR outFileName = "temp.bmp";
// Initialize GDI+.
GdiplusStartupInput gdiplusStartupInput;
ULONG_PTR gdiplusToken;
GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL);
USES_CONVERSION;
Gdiplus::Bitmap* pBitmap = new Gdiplus::Bitmap(T2W(fileName));
if (pBitmap==NULL || pBitmap->GetLastStatus() != Gdiplus::Ok) { logger.ERROR_F("转分辨率出错:" + to_string(pBitmap->GetLastStatus())); delete pBitmap; return FALSE; }
Gdiplus::Status status = pBitmap->SetResolution(dpi, dpi);//设置此 Bitmap 的分辨率。
if (status != Gdiplus::Ok) { logger.ERROR_F("转分辨率:" + to_string(status)); delete pBitmap; return FALSE; }
CLSID clsid;
GetEncoderClsid(L"image/bmp", &clsid); //Get the encoder
status = pBitmap->Save(T2W(outFileName), &clsid);//Save the image into physical memory
if (status != Gdiplus::Ok) { logger.ERROR_F("转分辨率后，保存错误:" + to_string(status)); delete pBitmap; return FALSE; }
delete pBitmap;
pipe_system("del "+ (CString)fileName+"\n", DELAY); //cmd先删除
pipe_system("rename " + (CString)outFileName + " "+ fileName +"\n", DELAY); //cmd重命名为原来的名
logger.INFO_F(string(fileName)+"设置分辨率成功:" + to_string(dpi));
return TRUE;
}
void PrintBitmap(LPCTSTR filename)
{
//setBMPResolution(filename, 600);//转为600分辨率
getBMPInfo(filename);
CPrintDialog printDlg(FALSE);
printDlg.GetDefaults();
CDC dc;
if (!dc.Attach(printDlg.GetPrinterDC())) {
AfxMessageBox(_T("No printer found!")); return;
}
dc.m_bPrinting = TRUE;
DOCINFO di;
// Initialise print document details
::ZeroMemory (&di, sizeof (DOCINFO));
di.cbSize = sizeof (DOCINFO);
di.lpszDocName = filename; //显示在打印列表里的名字
BOOL bPrintingOK = dc.StartDoc(&di); // Begin a new print job
// Get the printing extents
// and store in the m_rectDraw field of a
// CPrintInfo object
CPrintInfo Info;
Info.SetMaxPage(1); // just one page
//打印机页面的水平和垂直像素
int maxw = dc.GetDeviceCaps(HORZRES);
int maxh = dc.GetDeviceCaps(VERTRES);
//打印机每英寸像素数
int cxInch = dc.GetDeviceCaps(LOGPIXELSX);
int cyInch = dc.GetDeviceCaps(LOGPIXELSY);
logger.INFO_F("页面:" + to_string(maxw)+"*"+to_string(maxh) + " 打印机DPI:" + to_string(cxInch)+"*"+to_string(cyInch)); //mm 纸尺寸
Info.m_rectDraw.SetRect(0, 0, maxw, maxh);
for (UINT page = Info.GetMinPage(); page <=
Info.GetMaxPage() && bPrintingOK; page++) {
dc.StartPage(); // begin new page
Info.m_nCurPage = page;
CBitmap bitmap;
// LoadImage does the trick here, it creates a DIB section
// You can also use a resource here
// by using MAKEINTRESOURCE() ... etc.
if(!bitmap.Attach(::LoadImage(
::GetModuleHandle(NULL), filename, IMAGE_BITMAP, 0, 0,
LR_LOADFROMFILE | LR_CREATEDIBSECTION | LR_DEFAULTSIZE))) {
AfxMessageBox(_T("Error loading bitmap!")); return;
}
BITMAP bm;
bitmap.GetBitmap(&bm);//获得宽与高
// create memory device context
CDC memDC;
memDC.CreateCompatibleDC(&dc);
CBitmap *pBmp = memDC.SelectObject(&bitmap);
memDC.SetMapMode(dc.GetMapMode());
dc.StretchBlt(0, 0, bm.bmWidth * cxInch / 600 , bm.bmHeight * cyInch / 600 , &memDC, 0, 0, bm.bmWidth, bm.bmHeight, SRCCOPY);//按600dpi时的实际尺寸打印
//dc.BitBlt(0, 0, bm.bmWidth, bm.bmHeight, &memDC, 0, 0, SRCCOPY); //按图片大小打印
// clean up
memDC.SelectObject(pBmp);
bPrintingOK = (dc.EndPage() > 0); // end page
}
if (bPrintingOK)
dc.EndDoc(); // end a print job
else dc.AbortDoc(); // abort job.
}
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