<p>这里有一些东西,展示了绘制多色矩形水平和垂直渐变的方法。在</p>
<pre><code>from PIL import Image, ImageDraw
BLACK, DARKGRAY, GRAY = ((0,0,0), (63,63,63), (127,127,127))
LIGHTGRAY, WHITE = ((191,191,191), (255,255,255))
BLUE, GREEN, RED = ((0, 0, 255), (0, 255, 0), (255, 0, 0))
class Point(object):
def __init__(self, x, y):
self.x, self.y = x, y
@staticmethod
def from_point(other):
return Point(other.x, other.y)
class Rect(object):
def __init__(self, x1, y1, x2, y2):
minx, maxx = (x1,x2) if x1 < x2 else (x2,x1)
miny, maxy = (y1,y2) if y1 < y2 else (y2,y1)
self.min = Point(minx, miny)
self.max = Point(maxx, maxy)
@staticmethod
def from_points(p1, p2):
return Rect(p1.x, p1.y, p2.x, p2.y)
def __str__(self):
return 'Rect({:d}, {:d}, {:d}, {:d})'.format(self.min.x, self.min.y,
self.max.x, self.max.x)
width = property(lambda self: self.max.x - self.min.x)
height = property(lambda self: self.max.y - self.min.y)
def gradient_color(minval, maxval, val, color_palette):
""" Computes intermediate RGB color of a value in the range of minval
to maxval (inclusive) based on a color_palette representing the range.
"""
max_index = len(color_palette)-1
v = float(val-minval) / float(maxval-minval) * max_index
i1, i2 = int(v), min(int(v)+1, max_index)
(r1, g1, b1), (r2, g2, b2) = color_palette[i1], color_palette[i2]
f = v - i1
return int(r1 + f*(r2-r1)), int(g1 + f*(g2-g1)), int(b1 + f*(b2-b1))
def horz_gradient(draw, rect, color_func, color_palette):
minval, maxval = 1, len(color_palette)
delta = maxval - minval
for x in range(rect.min.x, rect.max.x+1):
f = (x - rect.min.x) / float(rect.width)
val = minval + f * delta
color = color_func(minval, maxval, val, color_palette)
draw.line([(x, rect.min.y), (x, rect.max.y)], fill=color)
def vert_gradient(draw, rect, color_func, color_palette):
minval, maxval = 1, len(color_palette)
delta = maxval - minval
for y in range(rect.min.y, rect.max.y+1):
f = (y - rect.min.y) / float(rect.height)
val = minval + f * delta
color = color_func(minval, maxval, val, color_palette)
draw.line([(rect.min.x, y), (rect.max.x, y)], fill=color)
color_palette = [BLUE, GREEN, RED]
region = Rect(0, 0, 730, 350)
imgx, imgy = region.max.x+1, region.max.y+1
image = Image.new("RGB", (imgx, imgy), WHITE)
draw = ImageDraw.Draw(image)
vert_gradient(draw, region, gradient_color, color_palette)
image.show()
#image.save("vert_gradient.png", "PNG")
#print 'image saved'
</code></pre>
<p>并显示图像:</p>
<p><a href="https://i.stack.imgur.com/BVwVI.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/BVwVI.png" alt="screenshot of gradient image created"/></a></p>
<p>这将在RGB颜色空间中插入中间颜色,但也可以使用其他颜色空间-有关示例,请参阅我对问题<a href="https://stackoverflow.com/questions/10901085/range-values-to-pseudocolor"><em>Range values to pseudocolor</em></a>的回答。在</p>
<p>这可以很容易地扩展到生成ARGB(Alpha+RGB)图像。在</p>