Question

所以...我写了这个代码，在Opengl中以正交模式绘制四边形。我知道它的位置和大小。有时是正方形...有时是矩形。我试图做的是放大和缩小并保持在四边形上的相同位置。我认为它会起作用，但事实并非如此。知道从鼠标位置到角落的距离，offset.x和等于rect_size.x- old_size_w的差异基本数学就是这样的：（offset.x / rect_size.x）*差异。这应该根据鼠标所处的位置给出我需要移动多少位置的比例。我希望有人可以解决这个问题.. 谢谢！....

一些数字......

     location = 100,100
     old_size_w = 1024
     rect_size.x = 1088 (new size old_ * 1.0625)
     mouse_delta.x = 425
     offset = 100 - 425 (-325)
     difference = 1088-1024 (64)
     delta_x = 325/1088 (.2987132....)
     x_offset = Cint(delta_x * difference) (19) (19.11764...)

所以....我们只移动了19个像素..如果我们从另一个方向做数学运算.. 2必须=与旧变焦和新变焦的差异

    delta_x = (1088-325) /1088 (.701286...)
    x_offset2 = Cint(delta_x * difference) (45) (44.88235...)
    19 + 45 = 64   <--- this proves out the math

然而......我正在变得越来越糟糕，越接近我移动的图像右侧。也许有人可以找到问题.. r_x在下面的代码中保留X并用于证明数学。

  Public Sub img_scale_up()
    If Not ready_to_render Then Return
    If Zoom_Factor >= 4.0 Then
        Zoom_Factor = 4.0
        Return 'to big and the t_bmp creation will hammer memory.
    End If
    Dim amt As Single = 0.0625
    Zoom_Factor += amt


    Dim offset As New Point
    'old_w and old_h are the orginal size of the image.

    Dim old_size_w, old_size_h As Double
    old_size_w = (old_w * (Zoom_Factor - amt))
    old_size_h = (old_h * (Zoom_Factor - amt))
    offset = rect_location - (mouse_delta)
    rect_size.X = Zoom_Factor * old_w
    rect_size.Y = Zoom_Factor * old_h
    Dim r_x As Double = ((rect_size.X - -offset.X) / rect_size.X) * (rect_size.X - old_size_w)
    Dim delta_x As Double = CSng(offset.X / rect_size.X)
    Dim delta_y As Double = CSng(offset.Y / rect_size.Y)
    Dim x_offset = delta_x * (rect_size.X - old_size_w)
    Dim y_offset = delta_y * (rect_size.Y - old_size_h)

    rect_location.X += CInt(x_offset)
    rect_location.Y += CInt(y_offset)

    draw_(current_image)

Answer 1

将鼠标位置存储为u，v，其中u和v为0.0 - 1.0。翻译你的图像，使其鼠标为0,0。操作，在这种情况下通过缩放。然后翻译回来，0，0，转到你。诉

Answer 2

好的..我把它排除了..我使用了几个错误的值来放大和缩小。这是用于围绕鼠标中心进行缩放并保持鼠标中心的整个代码。任何人都试图弄清楚这一点......这里的代码完美无缺：）

Public Sub img_scale_up()
    If Not ready_to_render Then Return
    If Zoom_Factor >= 4.0 Then
        Zoom_Factor = 4.0
        Return 'to big and the t_bmp creation will hammer memory.
    End If
    Dim amt As Single = 0.0625
    Zoom_Factor += amt

    'this bit of math zooms the texture around the mouses center during the resize.
    'old_w and old_h is the original size of the image in width and height
    'mouse_pos is current mouse position in the window.

    Dim offset As New Point
    Dim old_size_w, old_size_h As Double
    old_size_w = (old_w * (Zoom_Factor - amt))
    old_size_h = (old_h * (Zoom_Factor - amt))

    offset = rect_location - (mouse_pos)

    rect_size.X = Zoom_Factor * old_w
    rect_size.Y = Zoom_Factor * old_h

    Dim delta_x As Double = CDbl(offset.X / old_size_w)
    Dim delta_y As Double = CDbl(offset.Y / old_size_h)

    Dim x_offset = delta_x * (rect_size.X - old_size_w)
    Dim y_offset = delta_y * (rect_size.Y - old_size_h)

    rect_location.X += CInt(x_offset)
    rect_location.Y += CInt(y_offset)

    draw_(current_image)
End Sub

Public Sub img_scale_down()
    If Not ready_to_render Then Return
    If Zoom_Factor <= 0.25 Then
        Zoom_Factor = 0.25
        Return
    End If
    Dim amt As Single = 0.0625
    Zoom_Factor -= amt

    'this bit of math zooms the texture around the mouses center during the resize.
    'old_w and old_h is the original size of the image in width and height
    'mouse_pos is current mouse position in the window.

    Dim offset As New Point
    Dim old_size_w, old_size_h As Double

    old_size_w = (old_w * (Zoom_Factor - amt))
    old_size_h = (old_h * (Zoom_Factor - amt))

    offset = rect_location - (mouse_pos)

    rect_size.X = Zoom_Factor * old_w
    rect_size.Y = Zoom_Factor * old_h

    Dim delta_x As Double = CDbl(offset.X / (rect_size.X + (rect_size.X - old_size_w)))
    Dim delta_y As Double = CDbl(offset.Y / (rect_size.Y + (rect_size.Y - old_size_h)))

    Dim x_offset = delta_x * (rect_size.X - old_size_w)
    Dim y_offset = delta_y * (rect_size.Y - old_size_h)

    rect_location.X += -CInt(x_offset)
    rect_location.Y += -CInt(y_offset)

    draw_(current_image)
End Sub

Answer 3

在导出正确的方程式时，我经常迷路（做愚蠢的错误）（因为我使用了许多视图转换公式而不仅仅是一个）而且我大多数时候都懒得派生所以我这样做就是这样：

将鼠标位置转换为不缩放偏移量的坐标系

如果是屏幕或世界坐标系，则取决于您的转换顺序。将结果存储为mx0,my0
应用zoom更改
将鼠标位置转换为不缩放偏移量的坐标系

与＃1 相同，但更新为zoom。将结果存储为mx1,my1
更新偏移量

只需添加：
```
offset_x += mx0-mx1;
offset_y += my0-my1;
```
offset_x,offset_y保持您的视图偏移（位置）。

另见Zooming graphics based on current mouse position

放大和缩小并将当前像素保持在鼠标坐标处

3 个答案: