Updated Cheat Sheet (markdown)

Cheat-Sheet.md

@@ -96,8 +96,8 @@ When the given image is as same as `i`, DrawImage panics.
 
 `DrawImage` works more efficiently as batches when the successive calls of DrawImages satisfies the below conditions:
 
-* All render targets are same (A in A.DrawImage(B, op))
-* All render sources are same (B in A.DrawImage(B, op))
+* All render targets are same (`A` in `A.DrawImage(B, op)`)
+* All render sources are same (`B` in `A.DrawImage(B, op)`)
   * This is not a strong request since different images might share a same inner
     OpenGL texture in high possibility. This is not 100%, so using the same render
     source is safer.
@@ -115,18 +115,6 @@ For more performance tips, see [[Performance Tips]].
 type DrawImageOptions struct {
     // SourceRect is the region of the source image to draw.
     // If SourceRect is nil, whole image is used.
-    //
-    // It is assured that texels out of the SourceRect are never used.
-    //
-    // Calling DrawImage copies the content of SourceRect pointer. This means that
-    // even if the SourceRect value is modified after passed to DrawImage,
-    // the result of DrawImage doen't change.
-    //
-    //     op := &ebiten.DrawImageOptions{}
-    //     r := image.Rect(0, 0, 100, 100)
-    //     op.SourceRect = &r
-    //     dst.DrawImage(src, op)
-    //     r.Min.X = 10 // This doesn't affect the previous DrawImage.
     SourceRect *image.Rectangle
 
     // GeoM is a geometry matrix to draw.
@@ -169,3 +157,77 @@ const (
     FilterLinear Filter = Filter(graphics.FilterLinear)
 )
 ```
+
+## `ebiten.GeoM`
+
+```go
+type GeoM struct {
+    // contains filtered or unexported fields
+}
+```
+
+`GeoM` represents a matrix to transform geometry when rendering an image.
+
+The initial value is identity.
+
+### `(*ebiten.GeoM).Translate`
+
+```go
+func (g *GeoM) Translate(tx, ty float64)
+```
+
+`Translate` translates the matrix by (`tx`, `ty`).
+
+### `(*ebiten.GeoM).Scale`
+
+```go
+func (g *GeoM) Scale(x, y float64)
+```
+
+`Scale` scales the matrix by (`x`, `y`).
+
+### `(*ebiten.GeoM).Rotate`
+
+```go
+func (g *GeoM) Rotate(theta float64)
+```
+
+`Rotate` rotates the matrix by `theta`. The unit is radian.
+
+## `ebiten.ColorM`
+
+```go
+type ColorM struct {
+    // contains filtered or unexported fields
+}
+```
+
+`ColorM` represents a matrix to transform coloring when rendering an image.
+
+`ColorM` is applied to the straight alpha color while an Image's pixels' format is alpha premultiplied. Before applying a matrix, a color is un-multiplied, and after applying the matrix, the color is multiplied again.
+
+The initial value is identity.
+
+### `(*ebiten.ColorM).Scale`
+
+```go
+func (c *ColorM) Scale(r, g, b, a float64)
+```
+
+`Scale` scales the matrix by (`r`, `g`, `b`, `a`).
+
+### `(*ebiten.ColorM).Translate`
+
+```go
+func (c *ColorM) Translate(r, g, b, a float64)
+```
+
+`Translate` translates the matrix by (`r`, `g`, `b`, `a`).
+
+### `(*ebiten.ColorM).ChangeHSV`
+
+```go
+func (c *ColorM) ChangeHSV(hueTheta float64, saturationScale float64, valueScale float64)
+```
+
+`ChangeHSV` changes HSV (Hue-Saturation-Value) values. `hueTheta` is a radian value to rotate hue. `saturationScale` is a value to scale saturation. `valueScale` is a value to scale value (a.k.a. brightness).