Raster image incorrectly rendered

[yixuan]

Hi, from another thread (yixuan/showtext#33 (comment)) I found a potential bug of ragg for the raster device function. Below are some minimal examples to reproduce:

mat = matrix(c("#FF000011", "#FF000066", "#FF0000AA", "#FF0000FF"), 2)
ras = as.raster(mat)

png("1.png", width = 200, height = 200)
par(mar = c(0, 0, 0, 0))
plot.new()
rasterImage(ras, xleft = 0, ybottom = 0, xright = 1, ytop = 1, interpolate = FALSE)
dev.off()

ragg::agg_png("2.png", width = 200, height = 200)
par(mar = c(0, 0, 0, 0))
plot.new()
rasterImage(ras, xleft = 0, ybottom = 0, xright = 1, ytop = 1, interpolate = FALSE)
dev.off()

ragg::agg_png("3.png", width = 200, height = 200, bitsize = 16)
par(mar = c(0, 0, 0, 0))
plot.new()
rasterImage(ras, xleft = 0, ybottom = 0, xright = 1, ytop = 1, interpolate = FALSE)
dev.off()

You can find that the second plot was incorrectly rendered.
The reason is that the raster data need to be converted to the proper type before passed to AGG, similar to the case of AggDevice16. This patch should fix this.

[thomasp85]

Thanks - I was sure I had tested this codepath, but apparently not :-)

[yixuan]

In fact I had very little knowledge about AGG. I just mimicked the code in AggDevice16 and fortunately it worked. 😄