请教用gdi+如何修改图片大小？最好发个示例，谢谢

[此贴子已经被作者于2022-5-9 07:58编辑过]

*用来改变现有图像的尺寸
*******************************************
*算法制作:行者孙(QQ:310727570)
*******************************************
*VFP应用程式算法群:12787940
*******************************************
FUNCTION resizeimage(pSourceFileNAme as String,pNewFileNAme as String,nWidth as Long,nHeight as long)
PRIVATE pSourceFileNAme,pNewFileNAme,nWidth,nHeight
DECLARE INTEGER GdiplusStartup IN gdiplus;
   INTEGER @token, STRING @INPUT, INTEGER OUTPUT
DECLARE INTEGER GdipSaveImageToFile IN gdiplus.DLL ;
   INTEGER nImage, STRING wFilename, STRING qEncoder, INTEGER nEncoderParamsPtr
DECLARE INTEGER GdipLoadImageFromFile IN gdiplus.DLL ;
   STRING wFilename, INTEGER @nImage
DECLARE INTEGER GdipGetImageGraphicsContext IN gdiplus.DLL ;
   INTEGER nImage, INTEGER @ nGraphics
DECLARE INTEGER GdipCreateBitmapFromScan0 IN gdiplus.DLL ;
   INTEGER nWidth, INTEGER nHeight, INTEGER nStride;
   , INTEGER nPixelFormat ;
   , STRING @ cScan0, INTEGER @ nImage
DECLARE INTEGER GdipDrawImageRect IN gdiplus.DLL ;
   INTEGER nGraphics, INTEGER nImage, SINGLE,SINGLE,SINGLE,SINGLE
DECLARE INTEGER CLSIDFromString IN ole32 STRING lpsz, STRING @pclsid
DECLARE INTEGER GdiplusShutdown IN gdiplus INTEGER token
DECLARE integer GdipDisposeImage IN gdiplus  long

 

LOCAL hToken, cInput
hToken = 0
cInput = PADR(CHR(1), 16, CHR(0))
GdiplusStartup(@hToken, @cInput, 0)

LOCAL nImage
nImage = 0
GdipLoadImageFromFile(STRCONV(pSourceFileNAme + CHR(0), 5), @nImage)
#DEFINE   GDIPLUS_PIXELFORMAT_32bppARGB          0x0026200A

LOCAL nBitmap, nWidth, nHeight, nX, nY
nBitmap = 0
nX = 0
nY = 0
GdipCreateBitmapFromScan0(nWidth, nHeight, 0, GDIPLUS_PIXELFORMAT_32bppARGB, 0, @nBitmap)

LOCAL nGraphics
nGraphics = 0
GdipGetImageGraphicsContext (nBitmap, @nGraphics)

GdipDrawImageRect(nGraphics, nImage, nX, nY, nWidth, nHeight)
LOCAL lcEncoder
lcEncoder = REPLICATE(CHR(0),16)

*CLSIDFromString(STRCONV("{557CF401-1A04-11D3-9A73-0000F81EF32E}" + CHR(0), 5), @lcEncoder)

ERASE (pNewFileNAme)
*GdipSaveImageToFile (nBitmap, STRCONV(pNewFileNAme,5) + CHR(0), lcEncoder, 0)
GdipSaveImageToFile (nBitmap, STRCONV(pNewFileNAme,5) + CHR(0), 0h00F47C55041AD3119A730000F81EF32E, 0)
GdipDisposeImage(@nImage)


GdiplusShutdown(hToken)

 

CLEAR DLLS
ENDFUNC

* 解压此文件到当前目录 引用前辈的解法。  需要 _gdiplus 文件支持  需要源图片文件 D:\TEST.jpg

PUBLIC oform1

oform1=NEWOBJECT("form1")
oform1.Show
RETURN


    **************************************************
*-- Form:         form1 (c:\users\administrator\documents\visual foxpro 项目\suofang.scx)
*-- 父类:  form
*-- 基类:    form
*-- 时间戳:   05/11/22 12:12:08 AM
*
DEFINE CLASS form1 AS form


    Top = 122
    Left = 400
    Height = 266
    Width = 400
    ShowWindow = 2
    DoCreate = .T.
    Caption = "Form1"
    WindowState = 0
    Name = "Form1"


    ADD OBJECT text3 AS textbox WITH ;
        FontSize = 12, ;
        Alignment = 3, ;
        Value = 120, ;
        Height = 24, ;
        Left = 108, ;
        Top = 60, ;
        Width = 100, ;
        Name = "Text3"


    ADD OBJECT text4 AS textbox WITH ;
        FontSize = 12, ;
        Alignment = 3, ;
        Value = 120, ;
        Height = 24, ;
        Left = 108, ;
        Top = 84, ;
        Width = 100, ;
        Name = "Text4"


    ADD OBJECT text5 AS textbox WITH ;
        FontSize = 12, ;
        Alignment = 3, ;
        Value = 72, ;
        Height = 24, ;
        Left = 108, ;
        Top = 120, ;
        Width = 100, ;
        Name = "Text5"


    ADD OBJECT command1 AS commandbutton WITH ;
        Top = 156, ;
        Left = 108, ;
        Height = 25, ;
        Width = 96, ;
        FontSize = 12, ;
        Caption = "开始转换", ;
        Name = "Command1"


    ADD OBJECT label1 AS label WITH ;
        AutoSize = .T., ;
        FontSize = 12, ;
        BackStyle = 0, ;
        Caption = "长", ;
        Height = 20, ;
        Left = 60, ;
        Top = 60, ;
        Width = 18, ;
        Name = "Label1"


    ADD OBJECT label2 AS label WITH ;
        AutoSize = .T., ;
        FontSize = 12, ;
        BackStyle = 0, ;
        Caption = "宽", ;
        Height = 20, ;
        Left = 60, ;
        Top = 84, ;
        Width = 18, ;
        Name = "Label2"


    ADD OBJECT label3 AS label WITH ;
        AutoSize = .T., ;
        FontSize = 12, ;
        BackStyle = 0, ;
        Caption = "分辨率", ;
        Height = 20, ;
        Left = 36, ;
        Top = 120, ;
        Width = 50, ;
        Name = "Label3"


    ADD OBJECT image2 AS image WITH ;
        Height = 84, ;
        Left = 228, ;
        Top = 60, ;
        Width = 108, ;
        Name = "Image2"


    PROCEDURE Load
         
    ENDPROC


    PROCEDURE Unload
         
    ENDPROC


    PROCEDURE command1.Click
        Local lcFile_S, lcFile_T, lnW_T, lnH_T, lnXDpi_T, lnYDpi_T
        m.lcFile_S = 'D:\TEST.jpg'
        m.lcFile_T = 'D:\TEST1.jpg'

        IF FILE(m.lcFile_T)

        ELSE
        =MESSAGEBOX('D:\TEST1.jpg此文件不存在。',0,'转换')
        RETURN .f.
        ENDIF


        m.lnW_T = THISFORM.TEXT3.VALUE      && 目标图宽、高度
        m.lnH_T = THISFORM.TEXT4.VALUE
        m.lnXDpi_T = THISFORM.TEXT5.VALUE     && 目标图分辨率
        m.lnYDpi_T = THISFORM.TEXT5.VALUE
        Set Classlib To "_GDIPlus.Vcx" Additive
        oGraphics=CreateObject("gpGraphics")      && 创建工作图像
        oImage=CreateObject("gpImage")            && 源图
        oImage.CreateFromFile(m.lcFile_S)         && 从源图创建
        m.lnW = oImage.ImageWidth                 && 宽
        m.lnH = oImage.ImageHeight                && 高
        m.lnXDpi = oImage.HorizontalResolution    && 水平分辨率
        m.lnYDpi = oImage.VerticalResolution      && 垂直分辨率
        oBitMap=CreateObject("gpBitMap")          && 目标图
        oBitMap.Create(m.lnW_T, m.lnH_T)          && 按目标图大小创建
        oGraphics.CreateFromImage(oBitMap)               && 工作图像按目标图建立
        oBitMap.SetResolution(m.lnXDpi_T, m.lnYDpi_T)    && 设置目标图分辨率
        oGraphics.DrawImageScaled(oImage, 0, 0, m.lnW_T, m.lnH_T)    && 源图按指定矩形区域缩放
        m.lnQuality = 90  && 100                  && 图片保存质量
        oBitMap.SaveToFile(m.lcFile_T, oImage.GetEncoderCLSID("image/jpeg"), "quality="+Transform(m.lnQuality))    && 按源文件类型保存至目标文件
        Release oBitMap    && 释放
        Release oImage
        Release oGraphics
        Release Classlib _GdiPlus


        IF FILE(m.lcFile_T)
        thisform.image2.Picture=m.lcFile_T
        =MESSAGEBOX('转换成功',0,'转换成功')
        ELSE
        =MESSAGEBOX('转换不成功',0,'转换不成功')
        ENDIF
    ENDPROC


ENDDEFINE
*
*-- EndDefine: form1
**************************************************

谢谢
原图
转换后

右边和下边线少了

使用MyFll.Fll转换也是这个问题

100缩放到10，一定丢失了90，如果原来的只有1，再缩放到1%，丢是一定的啦

缩小丢失细节是算法问题，如果采用像素块rgb的平均值作为新像素的rgb值就可解决这一问题，个人看法，不一定对٩(๑^o^๑)۶

有没有高手能解决这个问题？

好吧，我承认：
我是高手，不小心泄露身份啦。
哈哈哈哈。
其实我用的是专业图像处理软件Photoshop CC（正版价格印象中是2975元）。
PS代表最专业、最正规的图像处理算法……
好吧，Photoshop将350x350像素的图片，自动缩小至40x40，肯定需要借助全宇宙最最最最先进的插值算法，删除掉将近90%的图片像素，那么，图像线条必定是有损的。
再专业、再高手也必然如此。
这问题其实跟“高手、低手”无关。
我只能说：
楼主，我觉得吧，你有必要稍稍学习一点点计算机图像处理方面的知识——哪怕是皮毛知识，也不必太专业那种。
因为楼主这个问题问得相当业余，相当无畏那种。
呵呵。