Fix wrong y-axis range in writeImage() on Windows

[nocd5]

for y := 0; y < height; y++ { height-y }
returns height ~ 1

[changkun]

It looks like some failure tests are real.

[nocd5]

I think a following code fix the problem.
But the test still be failed though (R,G,B,A) is matched.

diff --git a/clipboard_windows.go b/clipboard_windows.go
index b7a8d5e..70fbd18 100644
--- a/clipboard_windows.go
+++ b/clipboard_windows.go
@@ -145,7 +145,7 @@ func readImage() ([]byte, error) {
 			// xhat := (x + int(info.Width-3)) % int(info.Width)
 
 			xhat := (x + int(info.Width)) % int(info.Width)
-			yhat := int(info.Height) - y
+			yhat := int(info.Height) - 1 - y
 			r := data[idx+2]
 			g := data[idx+1]
 			b := data[idx+0]

--- FAIL: TestClipboard (0.75s)
    --- FAIL: TestClipboard/image (0.66s)
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (0,0), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (0,1), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (0,2), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (0,3), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
...
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (957,196), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (957,197), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:111: read data from clipboard contains too much inconsistent pixels to the previous written data, number of incorrect pixels: 189684

[nocd5]

I think a following code fix the problem. But the test still be failed though (R,G,B,A) is matched.

diff --git a/clipboard_windows.go b/clipboard_windows.go
index b7a8d5e..70fbd18 100644
--- a/clipboard_windows.go
+++ b/clipboard_windows.go
@@ -145,7 +145,7 @@ func readImage() ([]byte, error) {
 			// xhat := (x + int(info.Width-3)) % int(info.Width)
 
 			xhat := (x + int(info.Width)) % int(info.Width)
-			yhat := int(info.Height) - y
+			yhat := int(info.Height) - 1 - y
 			r := data[idx+2]
 			g := data[idx+1]
 			b := data[idx+0]

--- FAIL: TestClipboard (0.75s)
    --- FAIL: TestClipboard/image (0.66s)
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (0,0), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (0,1), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (0,2), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (0,3), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
...
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (957,196), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:102: read data from clipbaord is inconsistent with previous written data, pix: (957,197), got: {R:30 G:30 B:30 A:255}, want: {R:30 G:30 B:30 A:255}
        clipboard_test.go:111: read data from clipboard contains too much inconsistent pixels to the previous written data, number of incorrect pixels: 189684

Type is different.
Comapre with go-cmp

--- FAIL: TestClipboard (1.82s)
    --- FAIL: TestClipboard/image (1.71s)
        clipboard_test.go:103: User value is mismatch (-want +got):
              any(
            - 	color.NRGBA{R: 30, G: 30, B: 30, A: 255},
            + 	color.RGBA{R: 30, G: 30, B: 30, A: 255},
              )
        clipboard_test.go:103: User value is mismatch (-want +got):
              any(
            - 	color.NRGBA{R: 30, G: 30, B: 30, A: 255},
            + 	color.RGBA{R: 30, G: 30, B: 30, A: 255},
              )

[nocd5]

readImage() and clipboard_test.go are updated.
If you have better solution for the problem, please reject the PR.

[changkun]

What if we just update the test file?

[nocd5]

What if we just update the test file?

A type of img2.At() as got is color.RGBA and type of img1.At() as want is color.NRGBA.

So I tried to convert to RGBA64 and compare.
But RGBA64At() is not declared at go 1.16.
I'll compare R,G,B,A each value.

It seems img2.At() returns type vary depending the image has transparent color or not.
If it has transparent, returns color.NRGBA, else returns color.RGBA.
A png image for test has no transparent but img2.At() for out of range returns {R:0,G:0,B:0,A:0}.
So before my patch img2.At() returns color.NRGBA and test is passed.