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-- Demonstrate loading a PNG image three different ways. The third will
-- be skipped unless my 'memoryfile' module is installed, so the output
-- image will have either two or three copies of the wood pattern.
local Cairo = require "oocairo"
local PIC_FILENAME = "examples/images/wood1.png"
local PIC_WD, PIC_HT = 96, 96
local MARGIN = 10
local IMG_WD, IMG_HT = PIC_WD * 3 + MARGIN * 4, PIC_HT + MARGIN * 2
-- These three functions do the same thing (loading a PNG file and creating
-- a surface object from it), but in different ways. Loading directly from
-- a filename is convenient, but using a file handle is more flexible.
-- Loading from a string allows images from other libraries like GD to be
-- converted into Cairo objects without going through a temporary file.
local function load_pic_from_filename ()
return Cairo.image_surface_create_from_png(PIC_FILENAME)
end
local function load_pic_from_file_handle ()
local fh = assert(io.open(PIC_FILENAME, "rb"))
local surface = Cairo.image_surface_create_from_png(fh)
fh:close()
return surface
end
-- This one only works if the 'memoryfile' module is installed.
local function load_pic_from_string ()
local ok, MemFile = pcall(require, "memoryfile")
if ok then
local fh = assert(io.open(PIC_FILENAME, "rb"))
local picdata = fh:read("*a")
fh:close()
fh = MemFile.open(picdata)
return Cairo.image_surface_create_from_png(fh)
end
end
local surface = Cairo.image_surface_create("rgb24", IMG_WD, IMG_HT)
local cr = Cairo.context_create(surface)
for i, func in ipairs{ load_pic_from_filename,
load_pic_from_file_handle,
load_pic_from_string }
do
local surface = func()
if surface then
cr:set_source(surface, MARGIN * i + PIC_WD * (i - 1), MARGIN)
cr:paint()
end
end
surface:write_to_png("loading-images.png")
-- vi:ts=4 sw=4 expandtab
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