From 4563c13167deb97851397789bf2fb95bb44cf1ed Mon Sep 17 00:00:00 2001
From: kub <derkub@gmail.com>
Date: Wed, 20 Mar 2024 23:40:37 +0100
Subject: [PATCH] add reading scaled png images
---
readpng.c | 37 +++++++++++++++++++++++++++++++++++++
readpng.h | 1 +
2 files changed, 38 insertions(+)
diff --git a/readpng.c b/readpng.c
index d0714ed..08bf80d 100644
--- a/readpng.c
+++ b/readpng.c
@@ -67,6 +67,43 @@ int readpng(void *dest, const char *fname, readpng_what what, int req_w, int req
switch (what)
{
+ case READPNG_SCALE:
+ {
+ int height, width, x_ofs = 0, y_ofs = 0;
+ unsigned short *dst = dest;
+ int x_scale, y_scale, x_pos, y_pos; // Q16
+
+ if (png_get_bit_depth(png_ptr, info_ptr) != 8)
+ {
+ lprintf(__FILE__ ": scaled image uses %ibpc, needed 8bpc\n", png_get_bit_depth(png_ptr, info_ptr));
+ break;
+ }
+ width = png_get_image_width(png_ptr, info_ptr);
+ x_scale = width*65536 / req_w;
+ height = png_get_image_height(png_ptr, info_ptr);
+ y_scale = height*65536 / req_h;
+ if (x_scale < y_scale)
+ x_scale = y_scale;
+ else y_scale = x_scale;
+ x_ofs = req_w - width*65536 / x_scale;
+ y_ofs = req_h - height*65536 / y_scale;
+
+ dst += y_ofs/2*req_w + x_ofs/2;
+ for (y_pos = 0; y_pos < height*65536; y_pos += y_scale+1)
+ {
+ unsigned char *src = row_ptr[y_pos >> 16];
+ int len = 0;
+ for (x_pos = 0; x_pos < width*65536; x_pos += x_scale+1, len++)
+ {
+ int o = 3*(x_pos >> 16);
+ // TODO: could use bilinear if upsampling?
+ *dst++ = PXMAKE(src[o], src[o+1], src[o+2]);
+ }
+ dst += req_w - len;
+ }
+ break;
+ }
+
case READPNG_BG:
{
int height, width, h, x_ofs = 0, y_ofs = 0;
diff --git a/readpng.h b/readpng.h
index 4bb7ba7..c3d58a7 100644
--- a/readpng.h
+++ b/readpng.h
@@ -7,6 +7,7 @@ typedef enum
READPNG_FONT,
READPNG_SELECTOR,
READPNG_24,
+ READPNG_SCALE,
}
readpng_what;
--
2.39.5