From 8bee2894351444d5a7ef132fa7e1213c48d41ebf Mon Sep 17 00:00:00 2001
From: treeform <starplant@gmail.com>
Date: Mon, 1 Aug 2022 17:07:48 -0700
Subject: [PATCH] Add cropAlpha.

---
 src/pixie/images.nim       |  30 ++++++++++++++++++++++++++++
 tests/images/cropHeart.png | Bin 0 -> 1067 bytes
 tests/test_images.nim      |  39 +++++++++++++++++++++++++++++++++++++
 3 files changed, 69 insertions(+)
 create mode 100644 tests/images/cropHeart.png

diff --git a/src/pixie/images.nim b/src/pixie/images.nim
index eef3c14..3af36ca 100644
--- a/src/pixie/images.nim
+++ b/src/pixie/images.nim
@@ -751,5 +751,35 @@ proc superImage*(image: Image, x, y, w, h: int): Image {.raises: [PixieError].}
     result = newImage(w, h)
     result.draw(image, translate(vec2(-x.float32, -y.float32)), OverwriteBlend)
 
+proc cropAlpha*(image: Image): (Image, Rect) =
+  ## Crops the alpha off the edges of an image.
+  ## Returns the new cropped image and the rectangle it used for cropping.
+  var
+    xMin = image.width
+    xMax = 0
+    yMin = image.height
+    yMax = 0
+  # Find the crop coordinates.
+  for y in 0 ..< image.height:
+    for x in 0 ..< image.width:
+      if image.unsafe[x, y].a != 0:
+        xMin = min(xMin, x)
+        xMax = max(xMax, x + 1)
+        yMin = min(yMin, y)
+        yMax = max(yMax, y + 1)
+  if xMax <= xMin or yMax <= yMin:
+    raise newException(PixieError, "Cannot cropAlpha fully transparent image")
+  let
+    corpImage = newImage(xMax - xMin, yMax - yMin)
+    cropRect = rect(
+      xMin.float32,
+      yMin.float32,
+      corpImage.width.float32,
+      corpImage.height.float32
+    )
+  # Draw the bigger image into the cropped image.
+  corpImage.draw(image, translate(vec2(-xMin.float32, -yMin.float32)))
+  return (corpImage, cropRect)
+
 when defined(release):
   {.pop.}
diff --git a/tests/images/cropHeart.png b/tests/images/cropHeart.png
new file mode 100644
index 0000000000000000000000000000000000000000..ea21adbf3405d194da0cdcaddccb450bbfb43241
GIT binary patch
literal 1067
zcmV+`1l0S9P)<h;3K|Lk000e1NJLTq001xm001xu1^@s6R|5Hm000B>Nkl<ZcmdU!
z&ubKC9LAsTJF_eOWiLW3_TE3h_RvFcvzNAlB85t?9z@Vk$feNi!7XlnNuh`>Mh_Cu
zo8UpjwrY|^C?Vj*Lv2ZE3@KF0>LHf6y4lQEp4pwHo9yn)?9Oa<KQQop-+8~!_jxj#
z&4x8-!Hd+_@0U`U;f?g@t&O3~{c<{^yjXLulo~z7Gc6=q!ro5x8wSvHW?wm-xs)`C
zN5<g1Kt2<}e$NeS?inLL@C?tg$Gh(b&$5TTo$7B3P#*f`;HKga0LKB?erBp?j&G{|
z&R%Y`f@h-CuM5D(3CK+d-fm^0AtLXvw=|SF+3-FPi+(LYIh{FV49-DBIIJy1#0bt)
zYimFE;?Q>ktPhU92jD7DS$7CEuU0i(s&y>-9EM#9`4+%#cUm;;u4=ke>sa*7i;pw=
zpg87EiW0>!{^aA<H};!)1QO`oCL97gk;Lb5>l;yg63$t0sLd;QM>wc$4CI4wZNZ^7
zuizcwpte!yK)ANxP@7lqj&M-h021V{ZJWruaIbg}h|RarLOk+ap}?0=-v&@<fiI!H
z4FE{N2z0e84?7lg)i}UnEZW^+(QG<SzB{v`$8wy!c_Tl$0)SUvA;5~{Cs+73O8W6B
zxSlHkRIV{aKVhn#-2m1B`)2^leH36B70;CblFd4*I^8b;M0J{;>DPS%#5Q_afFkQ2
z=cO@v+4EQnAhQ$CRP~B?qj%96diDI(0uW1+rvW@?-HQnD+;Woq|Gh?C0Lf>ch-$8O
zx7Se3(c}MZ)de7CPx71sORRed0hZ`(tEX)N<XX05tBh<txYHPw5qjI|V_N_s^SN6B
z%&_hS=!Kpdd1)Ac6zo^S0{q5$C!q&=Y38A6fW5cBTQ}ky1+d<%xeK@+=%v}LrU8h|
zPCRs=P1DB>XVXKgIV}T_<lOiSR4=mbDykRV**^FNAeJVF0lmSxJLrwdOn(9ekbJgm
z6^ma2xaTj~G50u&GlM7v3P5Dx`=VvahZT6hbsSKeGdL@#e&7H^?oO@QPU2Gm{^B}H
zsOf6oomvZ{8!7<dXAxs#Na21F7zxy(Cbh!~h7LgF_SoOHlNeOReXcu!8q}g@J34Iz
zAd=5MwM!dm0CQZo$s9GP)n<SD0f_v1_CIUaz(GK+a~%%3&R%MS>#L{jC*UDJef26g
zm-_;$7rZ@RRDWa-dwtLP&~X5g1sr>R{G=#O@cV4;HKD{a_WbxTdzzdHMI-?{togA^
zmY9@4{_*xaxW{`u<LyO3qydP`o>?#n=R<`qa7|dhv`QcG9@kM4c>p56j6Yub_s<ld
l)BN3F{nnkc+n!1kyauiDp~4^K2jTz#002ovPDHLkV1jXF1Q-AS

literal 0
HcmV?d00001

diff --git a/tests/test_images.nim b/tests/test_images.nim
index 70756cd..bbdb751 100644
--- a/tests/test_images.nim
+++ b/tests/test_images.nim
@@ -231,3 +231,42 @@ block:
   let image = newImage(100, 100)
   image.fill("white")
   doAssert image[10, 10] == rgba(255, 255, 255, 255)
+
+block:
+  # Make sure cropAlpha rases error.
+  let image = newImage(100, 100)
+  var hadError = false
+  try:
+    discard image.cropAlpha()
+  except PixieError:
+    hadError = true
+  doAssert hadError
+
+block:
+  # Make sure cropAlpha does nothing to full images.
+  let image = newImage(100, 100)
+  image.fill(rgbx(255, 255, 255, 255))
+  let (crop, rect) = image.cropAlpha()
+  doAssert crop.width == image.width
+  doAssert crop.height == image.height
+  doAssert rect == rect(0.0, 0.0, 100.0, 100.0)
+
+block:
+  let image = newImage(100, 100)
+  image.fillPath(
+    """
+      M 20 60
+      A 40 40 90 0 1 100 60
+      A 40 40 90 0 1 180 60
+      Q 180 120 100 180
+      Q 20 120 20 60
+      z
+    """,
+    parseHtmlColor("#FC427B").rgba,
+    scale(vec2(0.3, 0.3))
+  )
+  let (crop, rect) = image.cropAlpha()
+  doAssert crop.width == 48
+  doAssert crop.height == 48
+  doAssert rect == rect(6.0, 6.0, 48.0, 48.0)
+  crop.xray("tests/images/cropHeart.png")